automation still calls for human review

I received a (paper) letter today from a health provider I use routinely. It said that in an internal audit they found that they had overcharged me, and so were enclosing a check for the over-payment.

It was for $0.02.

Did crediting my account not even occur to them? Or is there some law that requires them to send a refund, even when it produces silly results?

There's probably some interesting psychology in my response. Charities (that spend more money on fundraising than on their stated causes) sometimes send physical letters with coins visibly taped to them, I guess to get people to open the envelope. I open the ones with nickels and dimes but toss the ones with pennies. But I scanned the check.