To round up is to raise a number to the nearest convenient one. Round up to the nearest pound, round up the total.
The convention is that a five rounds up, which is a rule rather than a fact. A charity box asks you to round up the bill, which is the commonest place people meet the phrase.
1phraseround upTo raise a number to the nearest convenient one.
“Round up to the nearest ten and it comes to ninety.”
round up is a phrase.
Practised in Numbers & Measurement