It's not a priority for me though it's not an unreasonable thing to do.
 A basic 5th grade exercise is ordering fractions, sometimes with their
decimal equivalents:    Fraction(1,3) < Decimal('0.4') < Fraction(1,2).
 I don't care if that gets done.  

If you do decide to do fractions too, the responsibility should be with
the fractions class (since decimals convert to fractions exactly but not
vice-versa).