1. If the digit coming after the desired number of significant figures happens to be more than 5, the preceding significant figure is increased by one,
2. If the digit involved is less than 5, it is neglected and the preceding significant figure remains unchanged.
3. If the digit happens to be 5, the last mentioned or preceding significant figure is increased by one only in case it happens to be odd. In case of even figure, the preceding digit remains unchanged.
