When rounding decimals, the number value of the last retained decimal is increased by 1 if the number in the next decimal place is 5 or greater. If the next decimal is less than 5, the number value of the last retained decimal simply remains the same.
For example, the decimal 64.225 rounded to the nearest tenth is 64.2, since the .2 in the hundredths place is less than 5. The same figure rounded to the nearest hundredth would read 64.23, as the number in the thousandths place is 5.
Likewise, rounding 108.618 to the nearest tenth would result in rounding to 108.6, as the next decimal place is 1, which is less than 5. Rounding the figure to nearest hundredth would read 108.62, as the number in the thousandths place is 8, which is greater than or equal to 5.