» Summing Rounded Numbers

Problem:

Cells B2:B4 contain several numbers with two decimal places. Cell B5 contains a SUM formula, which adds the values in cells B2:B4.
Cells C2:C4 contain exactly the same numbers as cells B2:B4, but the cells are formatted to display 0 decimal places.
When comparing the result of the SUM formula in cell C5 (7) with the apparent sum of the numbers shown above (6), it appears that the sum calculated by the formula is incorrect.
A similar problem occurs in columns D & E. Column E contains the same numbers as those listed in column D, except that they are formatted as thousands.
The result of the SUM formula in cell E5, adding cells E2:E4, does not match the apparent sum of those numbers.

Solution:

Round all the numbers in cells C2:C4 to the nearest integer prior to summing them.
Use the SUM and ROUND functions in following Array formula:
{=SUM(ROUND(C2:C4,0))}
Round all the numbers in column cells E2:E4 to thousands prior to summing them.
Use the SUM and ROUND functions in the following Array formula:
{=SUM(ROUND(E2:E4,-3))}