I used to manage a group of cashiers at a national grocery chain.
If you are afraid of cash handling, perhaps a different job would be better for you. There is no shame in knowing your limits, and what you do and do not have the talent to do. I have seen very confident cashiers get scammed out of $100+ by con-artists, while not having a clue as to what was going on. While being afraid of cash handling might make you more vigilant than they were, fear is often something that hobbles a person at just the wrong time. And when the scammer comes through your lane (as they will), you will need to face that without fear if you are to succeed.
I wouldn’t want someone afraid of driving to be driving my bus. It’s better to know beforehand. But if you think you might end up having to be a cashier someday anyway, you may want to practice somehow. And you should also receive training for at least a week at a new cashier job, alongside an experienced worker (any less, and the management is substandard). For most people, it’s not a scary thing, true – but if it is scary for you, there might be something to listen to in that warning.