There are a few more tricks as well, for instance:
When a customer is leaving the counter and another is approaching, you have time to return a tape to half of the shelves inside the store without it having any effect on efficiency and allowing you to clear 2 tapes of the counter at one time. if you have the storage shelf upgrade then you can even store rewound tapes that are further away for when RNG is smiling on you and you've managed to clear the queue more.
Unfortunately I don't expect players to discover all these little nuances during a game jam though as they will only be playing for 5-10 mins max.