Thanks for your suggestion. Maybe we can extend the existing function floor(x) and ceil(x) to pass a number of digits like round(x, n). Or we could extend round to allow passing rounding options like UP, DOWN, etc.
You can configure to use BigNumber (better anyway to use that for finanical data than regular numbers because regular numbers suffer a lot from round-off errors). The BigNumber library integrated in mathjs is powered by https://github.com/MikeMcl/decimal.js, which allows to configure different rounding options. So you could write a wrapper function to use that I think.