Honesty does pay, but not in the name of Jehovah. It is one thing to honestly correct a mistake a clerk makes when they give you too much change. I do that occasionally, when I get too much back. But I will never count it as "selling Jehovah's name for a quarter"--if that was all there was, I would sell His name for a penny.
But, there is a limit. If I am right there, and see the mistake, I will report it--this helps the stores keep prices down, plus it might help the clerk to avoid becoming unemployed (and, if it's $20 or more, and you don't catch it but they do, you could be in trouble for petit larceny if you keep it). But, if no one catches the mistake by the time I have left the store, I will not go back in just to return the extra change. Usually, this will be caught when I get home from the store, and that is too late. And, if I "sell Jehovah's name for a penny", too bad--it isn't even worth that much.