The storage of cash situation is is a weird one nobody really talks about. It's unclear to me how Posabit gets USD back to the retailer, but my understanding is the funds moving from Posabit to retailers happens as USD.

Due to the fact retailers have to move large sums of cash, and can't store it in a bank easily, they're pretty tight lipped about the situation (pot shops being robbed at the end of the night isn't unheard of).