The purpose of this option is to add special "<Rounding>" postings, to
ensure that a regiter's running total is *always* the sum of its
postings. Within --rounding, these adjustment postings are missing,
which was the behavior in Ledger 2.x. It can be orders of magnitude
slower to turn it on for large reports with many commodities.
This way, if the running total is off by a penny or two due to rounding
of one or more commodities in the account, the user will see it.
This commit also reorganizes the testing code a bit, which I did after
adding the ninth test series (ConfirmTests), to validate the new
rounding code.
