Thanks Sue.

Yes... I had already found this on a census site. It may help future researchers

1841: For this census ages up to 15 were reported exactly. Ages from 15 and over were rounded down to the nearest 5 years

Looking at the years posted for my question it looks like this was the rule, but not everyone complied.

With 13 x year ages at 5 or 0, but 3 x year ages on other numbers.
Looks like most people followed this instruction but not everyone.