餐厅计费程序功能

我需要制作一个餐厅账单计算器程序，允许人们从菜单项列表中进行选择（一个函数），直到他们有了想要点的所有菜，然后在从列表中完成选择后计算总数。然后，它取他们投标的金额，减去总额加上税款和小费来计算变化。

我在这里和其他地方找到了一些想法和类似的项目，但没有什么能让我对如何最终确定这个项目有足够好的想法。我已经对程序进行了编码，但我不知道如何获取运行总数并不断累积，直到用户输入"8"。我有一个正常运行的程序，但它在每次选择后都会进行汇总，而不是保持一个运行的汇总，并在用户按"8"键结束时进行计算。

看看下面，如果你愿意的话，看看你是否能把我的方向指向正确的方向。基本上，这个任务是关于函数的，所以我们被要求使用函数来显示菜单并计算总数。

#include <iostream>
#include <iomanip>
using namespace std;
// Function Prototypes
void showMenu();
void showFees(double, int);
int main()
{
    int choice; //To Hold Menu Choice
    double quantity = 1;


    //contants for menu choices
    const int hamburgerChoice = 1;
    const int hotdogChoice = 2;
    const int peanutsChoice = 3;
    const int popcornChoice = 4;
    const int sodaChoice = 5;
    const int chipsChoice = 6;
    const int waterChoice = 7;
    const int endOrderChoice = 8;
    //constants for menu prices
    const double hamburger = 6.00;
    const double hotdog = 4.50;
    const double peanuts = 3.75;
    const double popcorn = 5.50;
    const double soda = 2.80;
    const double chips = 1.00;
    const double water = 2.00;
    //set precision
    cout << fixed << showpoint << setprecision(2);
    do
    {
        //display menu and get user choice
        showMenu();
        cin >> choice;
        //validate choice
        while (choice < hamburgerChoice || choice > endOrderChoice)
        {
            cout << "Please enter a valid menu choice: ";
            cin >> choice;
        }
        //if the user does not want to quit proceed
        if (choice != endOrderChoice)
        {
            //display fees
            switch (choice)
            {
                case hamburgerChoice:
                    showFees(hamburger, quantity);
                    break;
                case hotdogChoice:
                    showFees(hotdog, quantity);
                    break;
                case peanutsChoice:
                    showFees(peanuts, quantity);
                    break;
                case popcornChoice:
                    showFees(popcorn, quantity);
                    break;
                case sodaChoice:
                    showFees(soda, quantity);
                    break;
                case chipsChoice:
                    showFees(chips, quantity);
                    break;
                case waterChoice:
                    showFees(water, quantity);
                    break;
            }
                    }
    }
    while (choice != endOrderChoice);
    system("pause");
    return 0;
}
//*************************************************************
//Definition of function showMenu which displays the menu    **
//*************************************************************
void showMenu()
{
    cout << "nttBaseball Game Snacks" << endl;
    cout << "1. Hamburger t$6.00"<< endl;
    cout << "2. Hotdog tt$4.50" << endl;
    cout << "3. Peanuts tt$3.75" << endl;
    cout << "4. Popcorn tt$5.50" << endl;
    cout << "5. Soda tt$2.80" << endl;
    cout << "6. Chips tt$1.00"<< endl;
    cout << "7. Water tt$2.00" << endl;
    cout << "8. END ORDER" << endl;
    cout << "Please enter your menu choice: ";
}
//************************************************************
//Definition of function showFees which caculates the total **
//bill                                                      **
//************************************************************
void showFees(double itemCost, int quantity)
{
    double amtTendered;
    double totalBill = (itemCost * quantity);
    double taxRate = .065;
    double tipRate = .20;
    double tip = (totalBill * tipRate);
    double tax = (totalBill * taxRate);
    double amountDue = (totalBill + tax + tip);
    cout << "Total Bill: $" << totalBill << endl;
    cout << "Tax: $" << tax << endl;
    cout << "Tip: $" << tip << endl;
    cout << "Total Amount Due: $" << amountDue << endl;
    cout << "Enter ammount tendered: $";
    cin >> amtTendered;
    double changeDue = amtTendered - amountDue;
    cout << "Change Due: $" << changeDue << endl;
}