I have heard about that before also. I think at our childcare, it's $15 per minute. Enough that if we get stuck in traffic, we call a relative and hope they can get there faster.
As said elsewhere, I don't think it's ever enforced, just as backup in case they have someone repeatedly taking advantage of them.
I've often arrived in the last 3-5 minutes. If you are late, staff are forced to hang around, cleaners potentially can't complete their job, etc.