How accurate can Taxcaster be? It does not allow you to enter your Fed tax with-held on Social Security nor does it deal with your Medicare costs.

With social security, you have your gross, your fed tax with-held, your Part B, and Part D.  Taxcaster never asks you for those - any of them other then your actual ssa gross.  Even if this was correct, how accurate is taxcaster if you answer all applicable questions?