There are more commonly-traded currencies, such as the Russian ruble and the old Brazilian cruzeiro, that have had hyperinflation in the recent past.

But you certainly could have a fast path for stable currencies that are very unlikely to hyperinflate (USD, EUR, GBP, JPY).

Disagree with that. Overflows and rounding errors are not to be taken lightly.

Of course overflow and rounding error must be accounted for in your data type. Exchanges have price boundaries, price quanta, or risk boundaries that would guide this decision. My point is that you would not rule out a data type for trading based on an obscure currency like the Zimbabwean dollar.