Would like to see an option so that economic drops can be rounded to the nearest whole number.

Set this option to true in the config:

System:
  Economy:
    IntegerCurrency: true

Ah yes but an option for whole numbers (0, 1, 2, 5, 21, 100) would be great.

ecoCreature hands off the actual formatting of the number to Vault and the economy plugin. What econ plugin are you using? Hopefully, there's an option to tweak the number format for that econ plugin.

Right now, Essentials

Yeah, I don't see any options for whole number formatting in the EssentialsEco docs. It's not supported.

Do you know one with whole number formatting?

I can't think of any with that specific feature but I'm partial to Craftconomy as an econ plugin in general.