So the problem isn't a lack of cashiers but a lack of cash. It seems like the problem could be solved by having a few smartphone-like devices that you can shop

So the problem isn't a lack of cashiers but a lack of cash. It seems like the problem could be solved by having a few smartphone-like devices that you can shop on and take to an automated cash machine at the end. Then you'd just need a supervisor to make sure people weren't walking off with the merch, which they probably have anyway.