What do shop assistants do when they need to go to the toilet?

I am thinking about this as I may end up with a shop assistant job.

I understood that they tell a co-worker where they are going to the toilet, go to the toilet and come back as fast as possible.

However, that works ok if you they need to go for a pee but what if they need to go for a poo. By the time you walk out of the shop, through the mall to the toilets, poo and come back it would be at least 10 minutes!