Truncation less than or equal to 4, carry with mantissa greater than or equal to 5. According to the query of bright life. Com, the cashier rounding algorithm is: when taking decimal divisor, if the highest digit of mantissa is 4 or less, the mantissa is removed; If the highest digit of the mantissa is 5 or above, the mantissa will be deleted and the first digit will be entered as 1.