Hi sjme,
The 1841 census round ages up to the nearest 5.
From scotland Peoples website,
"Enumerators were instructed to round down the ages of persons 15 years and over to the nearest five years. Hence a given age of 28 would be recorded as 25, one of 63 as 60 and so on. If a person lied about their age, this, combined with the rounding down, could severely distort the actual age. You will find instances where enumerators did not adhere to this instruction on age and inserted the given age."
Tom