While I admit I don't like being asked for a donation at checkout, at least if everyone in town is doing it, I still prefer that to Target's model. They do what you suggest and give their own money, but it's still mine in a way. I'd bet dollars to dimes everything they give money to is something a liberal would approve of, so it means that into every purchase I make is in effect built in a donation to a group supported by only half their customers. Better if they lower their prices by that percentage and maybe Cato, or GOA, or some conservative Congressional candidate might get the money instead of some home for hags that think all men are rapists because they have penii, yet somehow they're not all prostitutes.
Actually, the word penis is 3rd Declension Masculine, which means the plural would be penes. (Not to be picky, but I had three years of Latin.)