Maybe a bit of paranoia coupled with laziness.
It might have been near the end of his shift, so he's going to be lazy in regards to replenishing the floats because he has to count it. If he has to give change for a hundred, he had to break open bills or rolls to give you change. Plus he had to go ALL the way to the back....poor guy! In hotels the front desk staff are like that also, nothing is worse than having to break open rolls of dimes or pennies 5 minutes before the end of your shift, you have to count all the loose coins, and so does the person taking over your float.
I remember this stupid girl who was SO lazy, she would go to the waitresses in the restaurant to exchange loonies/toonies to get quarters because she was too lazy to break open a new roll. Bugged the $#it out of me
"All these years I thought it was power that brought responsibility. It's not. I was wrong. It's responsibility that brings power. It's knowing what needs to be done that brings strength. And courage." - Peter Parker, Earth X