Decimal Function

As I said - post a sample - ie a file.

Those specific values would generate 088 therefore I suspect the cells (A1:A6) are in fact simply formatted to 3 decimal places.
As a result of which you are experiencing roundings, however, to verify to be the case we need to see a file containing the exact values you're summing.

To elaborate - a cell containing the value 62.49999999 formatted to 3 decimals will appear as 62.500 ... however when summed it is the underlying value that is used and not the formatted value*

The below

62.4999	62.500
62.4999	62.500
26.7381	26.738
26.3497	26.350
62.4999	62.500
62.4999	62.500

the values to the left would generate 087 for ex. even though the formatted values (right) would appear to total 088

If this is the issue we can account for it - but we need to see the file to be sure.

*unless using Precision as Displayed - not generally recommended