As a manager that has been in many similar situations working the drive thru, I've had complaints about my employees working the DT. It is absolutely no help to yell because it creates unneeded tension.
That said, I understand the mess. Somebody is ripping you off. Maybe a tiny bit, but it's the principle of the matter. That kid doesn't have much integrity doing what he is doing. If that happened where I work, we would move him off the register and to where there is no money handling, and, depending on the severity or amount, would get him audited. Yeah, my job doesn't play around.
Tick, as a manager for about 5 years in food service, I'd say next time just get the manager and be calm. I know it's such a stupid situation and can anger people, but a good manager will help you out. A bad manager? Then you call the corporate office and complain. Gah, I am too familiar with this...I've never had a complaint on me (because I know how to calm people down), but I have seen many managers get written up for not taking care of the customer.
Every customer is not worth saving.
Corporate higher-ups would like to have a word with you.
Oh, by the way, to me, it seemed like Tick was using "black" as a descriptor. Like, that was how we was able to see the pattern more easily in how his quarters were not being handed to him. All the black people I work with are cool and call me the "n" word all the time and I call them it also, and we pick on our Jewish employee and he's cool with it. One of the black girls said she'd have my baby, actually, so hey.