Rounding should be a FORMAT and not just a function. The Round() function does the job but it is tedious to use.
In the Format->Number, it should have another field for how many digits of rounding needed. For example -3 would round to 123,000.
Also, # of significant digits is critical. For financials, 3 significant digits is plenty. Sometimes only 2 is needed. If less than sqrt(10), then 3 digits, otherwise 2 digits is the best (2.5 significant digits).