Alex Andronov wrote:
In that document it says: "Excel 97, however, introduced an
optimization
that attempts to correct for this problem. Should an addition or
subtraction
operation result in a value at or very close to zero, Excel 97 and
later will
compensate for any error introduced as a result of converting an
operand to
and from binary. The example above when performed in Excel 97 and
later
correctly displays 0 or 0.000000000000000E+00 in scientific notation."

And you believe online help? That's somewhat unfair: note the keyword
'attempts'.

What it means is that if you enter the formula

=2.7-4.3+2.2+5.2-5.8

it does evaluate to zero. However, if these values are in different
cells, all bets are off. Interestingly, if you change the order of the
expressions so that the 5.2-5.8 expression doesn't come last, Excel
will return 0.

Getting back to the main point, use ROUND if you want a rounded result.
In this case, =ROUND(SUM(yourrange),6) would return 0.