Effective rounding can be used to communicate and present numbers so that they can be understood quickly and easily. Remove any unimportant or irrelevant information, but keep the detail in the data.
Look at whether there is a difference between the first numbers, second numbers, third numbers and so on. You should round the numbers for comparison to two effective digits.
When using effective rounding you may need an extra level of rounding when a value is small enough that the detail is removed when using two effective digits. If the value is not important it could be removed from the table. If it is important the level of effective rounding should be adjusted to an appropriate level.
Three levels of effective rounding
Not (no effective rounding)
Not (two levels of effective rounding)