Create a C$++$program that allows the user to enter an unknown number of sales amounts for each of three car dealerships: Dealership $1,$ Dealership $2,$ and Dealership $3.$ The program should calculate the total sales. Display the total sales with a dollar sign and $.$

Note: While a nested loop solution is not required it is beneficial to attempt such a solution.

Terminate your car dealership sale entries on any negative number. Do not generalize solution to accept N dealerships.