I know what you mean. When the cashier at Whole Foods asks you, it does feel somewhat petty to say no. I think there was a South Park episode on that.

But if the POS asks you, it doesn't feel as personal to turn down the option to donate, don't you think?

Anyway, not married to the idea, but I think there are some people that enjoy the endorphins that result from contributing to a charitable cause (especially when discretionary spending, like on a latte).

Nag-screens are awful but they do also need to explain their tipping because it creates customer confusion. They could simply put up a sign up that says "We pay our employees a living wage. We don't accept tips, but you can donate to our staff's preferred charity XYZ at URL."

> It was with small change but now McDonalds harasses you every time you make an order to round up for some charity I never heard about.

To be fair, the McDonalds charity is actually totally legit and really awesome and you should donate to it. It's one of the few exceptions to the general rule that these charity promotions are usually suspect tax laundering schemes.

You've never heard of the Ronald McDonald House?

> I'd donate to charities on my own.

But lots of people won't think to do so, and it can raise awareness too. And in terms of payment processing fees it is probably much more efficient to include a small amount extra in a larger preexisting transaction and pool it up across customers than if everyone were to go out and donate $0.50 or whatever on their own.