The proper way to round a number ending in 5 with nothing past it to the
previous digit is to round that digit to the nearest even number. Excel
doesn't do that; it uses the obsolete theory that always rounds up so 2.5,
which should round to 2, is being rounded to 3. This means that over time,
in financial uses, money will eventually be over-reported, and in scientific
uses, the amount of energy and matter will eventually be over-reported.
Current rounding theory is to round to the nearest even number so that,
statistically, half the time numbers will be rounded up and half the time
they will be rounded down, thus eliminating artificially high compounded
results.

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