And should not have been working on a register.
When I was in HS (long ago!), my boss put a trainee on the register next register and asked me to help him out - while I was running my own register. Two hours later, while I was on my break, I told my boss that the kid couldn't count change and that I couldn't run two registers. I showed that kid how to count change back at least 10 times - he just wasn't smart enough to get it. My boss took him off register, and assigned him to sweeping the floor. That he could do! Counting change is such a basic ability - I've often wondered what became of him.