For what it's worth, there is a method called "bucket rounding" that is often used
in transportation planning (but nowhere else according to
google)
which can help in this type of problem (within the limits of
machine precision). The process is very
simple: the "residue" from each rounding operation in a sequence
is retained to be applied as a bias to the next one. So
for
merlyn's
example:
# Value Residue Rounded Comment
1 10.3 0.0 10 0.3 is added to the residue
2 10.3 0.3 11 10.3 + 0.3 = 10.6, which rounds to
+11 with -0.4 residue
3 10.4 -0.4 10
==== ====
31.0 31
This is most commonly applied in the factoring of 2D matrices representing
trips from location to location. While the value of each cell is not
usually affected by a minor rounding error, the total of the matrix
needs to be held constant.
I'm certainly not qualified to say whether this
would be appropriate for financial work though.
--
I'd like to be able to assign to an luser