'they tell me I'm wrong, and I keep it'.
Also stealing. Actually even if they INSIST they are right, I go over it with them. Their mistake is no reason for me to keep it. People nearly always take a moment to see their error, so whatever they first say in response, I could care less, what matters is is the calculation correct or not - it's very, very simple. It always takes a moment to carefully go over the numbers and identify the error.
It is stealing - out of the store's pocket and the cashier's hide, and perhaps for the cashier, it can mean losing far, far more than the amount of the change.
In general, short comes out of the chashier's pay.
And in some places, a cashier will get fired if he closes short.
Say in her time at that store, she is allowed three short cashouts before she gets fired.
Say she's already made two errors. Just honest errors. Mistakes.
Say this is her first. If she can't explain it, she may not only get fired, she could get prosecuted.
Your friend's 'not stealing' could lose the cashier his/her job or more.
And in this market, she won't get another job for a long time. She could lose her house, everything.
I would like to emphasize that that practice is not typical of people who gross near 100K annually.
I made within a few k of that amount, and I would return a ball of lint or a penny, if it wasn't mine.
Big corporation, mom and pop store, kid's lemonade stand, I don't care. Employees of the big corporations usually have their feet held to the fire far quicker than the small businesses.
And I would do the same when I was making 80k, 60k, 50k, 20k, or 10k a year, or nothing at all. So would most of the people I know, janitor to CEO.
Your friend is dishonest. It's very simple.
I could never do that to anyone. My father and mother would roll over in their graves if I ever let anyone give me even a penny that I wasn't owed.
The money belongs to the store. But whose hide it will come out of - that's the cashier.