It's actually sort of the opposite. Interest based money is designed so that the numeric value grows over time. A tax on holdings makes its numeric value decrease over time. See http://en.m.wikipedia.org/wiki/Demurrage_(currency)
Both inflation and demurrage reduce the purchasing power of money held over time, but demurrage does so through fixed, regular fees while inflation does so through expansion of the money supply by a central monetary authority distributing newly issued currency or through endogenous money creation (such as fractional reserve banking).
