How to Round Numbers?
Decide which is the last digit to keep.
Leave it the same if the next digit is less than 5 (rounding down)
But increase it by 1 if the next digit is 5 or more (rounding up)
We have 4.5
If we want rounding to the whole, then we look at tenth. We have 5, therefore rounding up
4.5 ≈ 5
