I am creating a python tkinter program to calculate order total for meal purchase. It will not display the sub total, sales tax, and order total. Can you show my how to calculate the pricess correctly?

Parts of code:

def receipt$()$:

sub$\_$total, sales$\_$tax, order$\_$total $=$ calculate$\_$total$()$

# else statement to display a receipt message box if all input is valid

receipt$\_$message $=($f$"$Thank you for your order! Elli$-$May will see you soon!

$"$

f$"$

Name: $\{$first$\_$name$\_$entry.get$()\}\{$first$\_$name$\_$entry.get$()\}"$

f$"$

Phone Number: $\{$phone$\_$number$\_$entry.get$()\}"$

f$"$

Sandwich: $\{$sandwich$\_$selected.get$()\}"$

f$"$

Taco: $\{$taco$\_$selected.get$()\}"$

f$"$

Taco Toppings: $\{$none$\_$selected.get$()\}\{$pico$\_$selected.get$()\}\{$cheddar$\_$cheese.get$()\}"$

f$"\{$sour$\_$cream.get$()\}\{$pickled$\_$onions.get$()\}\{$jack$\_$cheese.get$()\}"$

f$"$

Combo: $\{$combo$\_$selected.get$()\}"$

f$"$

Side: $\{$side$\_$selected.get$()\}"$

f$"$

Drink: $\{$drink$\_$selected.get$()\}$

$"$

f$"$

Sub Total: $$\{$sub$\_$total:$\mathrm{.}2$f$\}"$

f$"$

Tax: $$\{$sales$\_$tax:$\mathrm{.}2$f$\}"$

f$"$

Total: $$\{$order$\_$total:$\mathrm{.}2$f$\}")$

messagebox.showinfo$("$Receipt$",$ receipt$\_$message$)$

def calculate$\_$total$()$:

$"""$ calculate$\_$total function to calculate total price of order $"""$

# declaring variables for meal calculations

sub$\_$total $=$ float$(0\mathrm{.}00)$

sales$\_$tax $=$ float$(0\mathrm{.}07)$

if sandwich$\_$selected.get$()!=$ sandwich$\_$options$[0]$:

sub$\_$total $+=$ sandwich$\_$prices

if taco$\_$selected.get$()!=$ taco$\_$options$[0]$:

sub$\_$total $+=$ taco$\_$prices

if combo$\_$selected $==$ "yes":

sub$\_$total $+=$ add$\_$combo

elif combo$\_$selected $=="$no$"$:

sub$\_$total $+=$ no$\_$combo

if side$\_$selected.get$()!=$ side$\_$options$[0]$ and combo$\_$selected.get$()!=$ "Yes":

sub$\_$total $+=$ side$\_$prices

if drink$\_$selected.get$()!=$ drink$\_$options$[0]$ and combo$\_$selected.get$()!=$ "Yes":

sub$\_$total $+=$ add$\_$drink

tax$\_$total $=$ sub$\_$total $+$ sales$\_$tax

order$\_$total $=$ sub$\_$total $+$ tax$\_$total

return sub$\_$total, tax$\_$total, order$\_$total

sandwich$\_$options $=["$No Sandwich", $"$BBQ Pulled Pork", "Slaw$-$py Sliders", $"$BBQ Beef Brisket", "Pork Wrangler", $"$BBQ Pork Sliders", "The Ringer", "Best of Both Worlds","Smoked Chicken", $"$BBQ Beef Brisket Sliders", "Chicken Sliders","Slaw$=$py Pork"$]$

# creating parallel list for sandwich prices

sandwich$\_$prices $=["0\mathrm{.}00","8\mathrm{.}00","10\mathrm{.}00","10\mathrm{.}00","9\mathrm{.}50","9\mathrm{.}00","11\mathrm{.}50","9\mathrm{.}00","9\mathrm{.}00","11\mathrm{.}00","9\mathrm{.}00","9\mathrm{.}50"]$

# declaring variable for sandwich$\_$options list

sandwich$\_$selected $=$ StringVar$()$

# setting default value of list

sandwich$\_$selected.set$($sandwich$\_$options$[0])$

taco$\_$options $=["$No Tacos","BBQ Brisket Tacos","Pork Tacos","Chicken Tacos"$]$

# creating a parallel list for taco prices

taco$\_$prices $=["0\mathrm{.}00","11\mathrm{.}00","9\mathrm{.}00","9\mathrm{.}00"]$

# declaring variable for taco$\_$options list

taco$\_$selected $=$ StringVar$()$

# setting default value of list

taco$\_$selected.set$($taco$\_$options$[0])$

topping$\_$options $=["$None$",$"Pico","Cheddar Cheese","Sour Cream","Pickled Red Onions","Jack Cheese"$]$ # toppings are not charged an additional fee they are created with checkbuttons

# combo option created with checkbutton

if combo$\_$selected $==$ "Yes":

add$\_$combo $=2\mathrm{.}00$

else:

no$\_$combo $=0\mathrm{.}00$

# if combo is selected $2\mathrm{.}00$ is added to taco or sandwich price and there is no charge for side and drink

side$\_$options $=["$No Side","Cole Slaw","Fries","Tator Tots","Potato Salad","Onion Rings"$]$

side$\_$prices $=["0\mathrm{.}00","3\mathrm{.}00","3\mathrm{.}00","4\mathrm{.}00","3\mathrm{.}50","4\mathrm{.}00"]$

# declaring variable for side$\_$options list

side$\_$selected $=$ StringVar$()$

# setting default value of list

side$\_$selected.set$($side$\_$options$[0])$

drink$\_$options $=["$No Drink","Water","Pepsi","Diet Pepsi","Sierra Mist","Mountain Dew","Diet Mountain Dew","Root Beer"$]$

# declaring variable for drink$\_$options list

drink$\_$selected $=$ StringVar$()$

# setting default value of list

drink$\_$selected.set$($drink$\_$options$[0])$

# declaring price of adding a drink:

add$\_$drink $=2\mathrm{.}00$