How to differentiate between ’round off’ and ’round up’

Are you among those who confuse ’round off’ with ’round up’? Then, this lesson is for you.
The fact is that many people do not know the difference between the two expressions. As a result, they use one where the other is ought to be.
What is the meaning of each of them? When are we supposed to use each? The video below, from Phenomenal English, answers these and more.