Unless your hardware implements BCD arithmetic, this method is pretty much guaranteed to be slower than just applying the MOD directly:

Direct calculation: 1 division

Proposed method: 1 division plus 1 bit shift plus 1 addition (per digit) plus 1 intermediate register finally one division

It doesn't matter whether division is implemented in hardware. On machines with BCD support, benchmarking would be required to see whether this method is beneficial.