IME, you only have to write the amount once for each cheque, and the total is written in the box on the front.
It's been a while since I had to do it, but I seem to recall, when paying in a single cheque:
- payer name + amount on the back of the slip
- total amount (i.e. the same again) at the bottom of the amount column on the back
- same amount next to the "total of cheques" label at the front
- same amount again for the total of cheques and cash
Perhaps I could skip one of these totals, but I'm afraid I won't get the money unless I complete the entire ritual.