That spare change you donate at checkout is adding up to millions for charities

So-called point-of-sale donations have sharply increased in recent years, bringing in hundreds of millions of dollars a year. But the requests to "round up" your bill for charity have really taken off. (Josie Norton for NPR)

We've all been there: A store cashier asks if you'd like to donate money to the local food bank. Or the PIN pad at the checkout counter prompts you to round up your payment for charity — spare a little change for a worthy cause.

Those "round-up" campaigns have become ubiquitous in recent years — at grocery chains, gas stations, retail stores and online merchants — and they rake in millions of dollars annually for everything from scholarships to cancer research.