public void RemoveNickels(int numberOfNickels)
 {
     for (int i = 0; i < numberOfNickels; i--)
     {
         Nickel nickel = new Nickel();
         nickels.Remove(nickel);
     }
 }
 public void AddNickles(int numberOfNickles)
 {
     for (int i = 0; i < numberOfNickles; i++)
     {
         Nickel nickel = new Nickel();
         nickels.Add(nickel);
     }
 }