When normal customers "find your behavior odd," the worst they'll do is not tip you. But when your customers are cops, they'll go through your surveillance feed. Lesson learned.
In case you missed it, it's been confirmed that Dunkin' Donuts sucks.
Although, to be fair, a friend of a friend did say there was some sort of cash-related scam going around that involved exchanging and re-exchanging coins. It was on TV. I didn't see the episode nor do I remember the show. So take that for what it's worth.