I've been at a bank that banned trial balances throughout the day. It was wasted work time. I had tellers that balanced when they came it, balanced after they ran the night-drop, balanced before they left for lunch, balanced after they came back, balanced at 2:00, balanced again at 3:00 when they went on "next-day", and then balanced again before they left. It was crazy! They were hardly ever off, and if they were it was rarely over $1. We had customers who had to wait in line because I always seemed to have one teller on the front line balancing.
The only time we allowed them to balance was at 3:00 when they closed out the day. They whined for the first week. But after that, it was a non-issue. And like I said, they were seldom off.
A good teller should not have to balance more than once a day, IMHO.