Choose the rounding digit -- the digit after the decimal point to which you want to round off the value. For instance, if the value is "16.8346" and you want to round if off to hundredths, then the rounding digit is "3." If you want to round the value off to thousandths, then the rounding digit is "4."
Keep the rounding digit as is and replace all the digits to its right with zero if the digit to the right of the rounding digit is less than 5.
Increase the rounding digit by 1 and replace all the digits to its right with zero if the digit to the right of the rounding digit is 5 or greater.