Go to the place value that you want to round to: for example, if we were rounding 3.46 to 1 decimal place accuracy we would go to the 4. Then look at the number after that (in this case a 6). If this is:

4 or less, round down
5 or more, round up

In this case we round up, because 6 is in the '5 or more' category. So 3.46 becomes 3.5 when rounded to 1 decimal place accuracy.

Significant figures are used in the rounding of answers to an appropriate degree of accuracy.

Example videos

Video: https://www.youtube.com/embed/IwdLT5Uz8XI