CL-USER> (lisp-implementation-version)
"Version 1.11.8 (v1.11.8-2-gd411e378) WindowsX8664"
CL-USER> (float 41107100000541273/100000000000)
411071.03

Hmm. If you work out the decimal points, the float is: 411071.00000541273, that's a long way from .03

Maybe coerce? Nope, that's even worse:

CL-USER> (coerce 41107100000541273/100000000000 'double-float)
411071.03125D0

Interestingly, taking one digit off the rational produces a correct result:

CL-USER> (float 4110710000054127/10000000000)
411071.0