I'd keep it. Call me a bad person or something. If life wants to tuck some extra money into my pocket, then so be it. I've had the situation reversed, where I was severely underchanged, and the involved retail establishment made no effort to correct their mistake. I would drive away with a smile on my face and a hamburger in my hand. In life, sometimes you win and sometimes you lose, unless you give back your wins, and then you just lose
Blingbling asks if my integrity is worth $40. My response to that is, "is a sense of moral righteousness worth paying $40 for?"