Quote Originally Posted by wysota
As far as I understand "round up" is an english expression (phrasal verb) which doesn't mean "round upwards" (just like "look up sth in the dictionary" doesn't tell you to look in the sky right?)
My dictionary says that when it comes to maths "to round up" means "to round upwards", in other contexts it behaves like you wrote.

but it can be misleading
Documentation shouldn't be misleading in any way.