I have a situation where I need to present a total dollar amount and a breakdown of that total.
The total is calculated as follows, rounded to 2 decimal places:
TotalQuantity * rate / #OfDaysInMonth
So for example:
Total $ Amount Rounded
------------------ -------------
17000 * 12.76919 / 31 = 7002.459032258 7002.46
Later on, I have a breakdown of the total quantity. The total quantity is broken into several individual quantities and calculated as follows, with each item rounded to 2 decimal places:
Quantity1 * rate / #OfDaysInMonth
Quantity2 * rate / #OfDaysInMonth
Quantity3 * rate / #OfDaysInMonth
...
QuantityN * rate / #OfDaysInMonth
For example:
$ Amount Rounded
------------------ -------------
600 * 12.76919 / 31 = 247.145612903 247.15
1000 * 12.76919 / 31 = 411.909354839 411.91
3000 * 12.76919 / 31 = 1235.728064516 1235.73
12400 * 12.76919 / 31 = 5107.676000000 5107.68
---------------------------------------------------------------------
Total: 17000 7002.459032258 7002.47
However, as you can see, the sum of the rounded individual amounts doesn't always add up to the rounded total amount.
Is there a way to make the rounded amounts add up to the rounded total?
I don't have access to the total amount or the total quantity at this point. I can't add up the individual quantities to get the total quantity. Neither can I calculate the rounded individual amounts first and then display the total amount from their sum.
I'm thinking maybe somehow I can manipulate the rounding so as to minimize the round-off errors but I'm not sure if this is the best strategy.