Program.cs

            decimal subtotal = 0;
            decimal price;
            string input;

            Console.WriteLine("Welcome to the Cashier Program!");

            // Input loop for item prices
            do
            {
                Console.Write("Enter item price (ex. 1.99) or press enter key if done: ");
                input = Console.ReadLine();

                if (decimal.TryParse(input, out price))
                {
                    subtotal += price;
                }
                else if (input != "")
                {
                    Console.WriteLine("Invalid input. Please enter a valid price.");
                }
            } while (input != "");

            // Calculate sales tax
            decimal salesTax = subtotal * 0.0615m;

            // Calculate total with tax
            decimal total = subtotal + salesTax;

            Console.WriteLine($"Subtotal is: {subtotal:C}");
            Console.WriteLine($"Sales tax is: {salesTax:C}");
            Console.WriteLine($"Total amount due: {total:C}");

            // Input for cash given
            decimal cash;
            do
            {
                Console.Write("Enter the cash given by the customer: ");
                input = Console.ReadLine();

                if (!decimal.TryParse(input, out cash) || cash <= 0)
                {
                    Console.WriteLine("Invalid input. Please enter a valid positive number.");
                }

            } while (!decimal.TryParse(input, out cash) || cash <= 0);

            // Calculate change
            decimal change = cash - total;

            // Calculate denominations
            int twenties = (int)(change / 20);
            change %= 20;
            int tens = (int)(change / 10);
            change %= 10;
            int fives = (int)(change / 5);
            change %= 5;
            int ones = (int)change;
            change -= ones;
            int quarters = (int)(change / 0.25m);
            change %= 0.25m;
            int dimes = (int)(change / 0.1m);
            change %= 0.1m;
            int nickels = (int)(change / 0.05m);
            change %= 0.05m;
            int pennies = (int)(change / 0.01m);

            // Output change
            Console.WriteLine($"Change: {twenties} $20s, {tens} $10s, {fives} $5s, {ones} $1s, {quarters} quarters, {dimes} dimes, {nickels} nickels, {pennies} pennies");

            Console.WriteLine("Thank you for using the Cashier Program!");