Oh, there was one time last year that the post office worker gave me I think a dollar too much. I was going to give it back but the lines were insanely long and I didn't realize until I was already out the door. I donated it but I still feel a bit guilty! I did go back to Target a few weeks ago when I realized the cashier had forgotten to ring something up.
I actually think the former is worse than the latter.
With the postal worker it'll probably mean that the balance on his cash register will be off at the end of the day, with the Target thing it would have just been missing inventory with no consequences to anybody (certainly not the cashier anyway).
I would have skipped the line though at the post office to give back the dollar.