Servicemembers Interest Rate Relief Act of 2005 - Amends the Servicemembers' Civil Relief Act to revise the six percent maximum annual interest rate to be charged on debts incurred by a servicemember, and his or her spouse jointly, before the servicemember enters into military service and continuing for the duration of such military service, to the lesser of: (1) six percent per year; or (2) the annual rate of interest that would otherwise apply, reduced by one percentage point (but not below zero).