The machines at my PO only take credit/debit cards, and can’t do a transaction less than 1.00. Everyone in the line I was in was ready, but the clerks were incredibly lackadaisical in handling and processing everything.
I’ve bought 1 cent stamps from the automated postal center machines, and yes it only takes credit/debit. Sorry but spend too much time at the post office to buy that everybody in a 25 person line is ready, generally at best you’re looking at 2 out of every 10 that are actually ready to ship, and they’re in and out in under a minute.