(((Maggie))) - I understand what you're saying. Where I work is extremely dysfunctional, and I can't even get reimbursed for the $1 I spent on dishwashing soap when we were out, one night.
The thing is, I have to work, and applying at other jobs hasn't led anywhere, so I'm working "accepting the things I cannot change". Not easy, in fact it's downright frustrating, but I can't change it.
I used to wait tables, and was amazed that some people didn't realize my hourly wage was only $3.13...I depended on tips. In your situation, if someone says "keep the change", I'm a bit cocky and would say "I appreciate it, but if the check has anything extra on it, my boss keeps it", in a very calm voice, but that's just me. I'm with ((BabyBlue)) - I make sure the person that I want to tip, GETS the darned tip.
Hugs and prayers,
Amy