It is often useful to quickly make approximate answers for calculations. Imagine you buy items for R34 and R58 and do not have time to accurately calculate R34 + R58. It can help you to know that you need to pay about R30 + R60, which is R90. 34 can be rounded off to the nearest multiple of ten, which is 30. 58 can be rounded off to 60. 55 is equally far from 50 and 60. People all over the world have agreed to round off "upwards" in a case like this, so 55 is normally rounded off to 60.
678 rounded off to the nearest multiple of ten is 680. 678 can also be rounded off to the nearest multiple of hundred, which is 700. 634 rounded off to the nearest multiple of hundred is 600. 634 rounded off to the nearest multiple of ten is 630.

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