As others are pointing out, decimal fidelity and "error" are different things. Any fixed point mantissa representation in any base has a minimal precision of o

As others are pointing out, decimal fidelity and "error" are different things. Any fixed point mantissa representation in any base has a minimal precision of one unit in its last place, the question is just which numbers are exactly representable and which results have only inexact representations that can accumulate error. BCD is attractive to human beings programming computers to duplicate algorithms (generally financial ones) intended for other human beings to execute using arabic numerals. But it's not any more "accurate" (per transistor, it's actually less accurate due to the overhead).