How to pass time at work when working in a (kind of) retail environment?

I work at a retail pharmacy in the dispensing section. When we have customers, it’s fine, but sometimes we go a few hours with only a couple of customers coming in. My higher ups often spend a lot of the shift just on their phone, but I’m not at that level and don’t want to risk getting in trouble.

How else can I pass time,(beyond organising paper work etc, which I have already done) ?

Thanks :)