It seems more like the customers are paying the homeless, and the supermarkets are just acting as brokers.

it's the same for bottle deposits in parts of Europe. anything in a plastic bottle costs an extra ~10c which you can retrieve by depositing the empty in a machine at the supermarket

in the UK, trolley deposits are much more expensive, at £1. people are more likely to retrieve a £1 than a quarter, but the atomic payout is ~5x higher, so I wonder which scenario yields better pay for the homeless