a perfect change
A perfect change is the exact amount of coins you carry so you can give the cashier the worst amount of change possible. It’s like a coin bomb you drop on the counter.
I gave the cashier a perfect change because I wanted to see if they could handle it.
I had a perfect change and I just had to use it because I was feeling mean.
I dropped my perfect change on the counter and walked away like I was doing them a favor.