0% risks stagnation, which means investment isn't envouraged or discouraged. Even 1% inflation slightly encourages investment, and really the scale only needs to be tipped a bit to keep the economy moving forward toward growth.
If you're talking about the natural costs of holding money, those are miniscule. If you're talking about a tax I don't see how it avoids debasing the currency, or is meaningfully different from inflation. It just makes things more complicated because people can attempt to avoid paying.
