Rounding is an accurate counting retention method, which is essentially the same as other methods. But the special point is that rounding can make the difference between the reserved part and the actual value not exceed half of the last order of magnitude. If there is a probability of 0 ~ 9, the total error of this retention method is the smallest for a large number of retained data. This is probably why we regard this method as the basic reservation method.
"Rounding" method:
Looks like one more digit than the reserved number. If the number on this number is "5" or greater, move forward one place. If the number on this digit is "4" or less, it will be discarded.
For example, 6.56, leaving one decimal place is 6.6. And 6.54, one decimal place is 6.5.
When taking decimal approximation, if the highest digit of mantissa is 4 or less, the mantissa is removed. If the highest digit of mantissa is 5 or more, the mantissa is rounded and "1" is input before it, which is called rounding method.
"Nine Chapters Arithmetic" also adopts the method of "rounding". When using the proportional method to find the vehicles that should be dispatched in each county, because the vehicles are integers, the calculation results are rounded off.