I wrestle with this all the time!
I think it comes down to this: why do you look at it? If you are looking at MMM's retirement curve, I think you are saving 5%. Maybe a little more, because I seem to remember that curve being (savings / after tax income). That specific curve assumes that if you are saving 5%, you are spending 95%. If you are saving 60%, you are spending 40%. The scenario you have violates that 100% of after tax income assumption.
If you just want to know because it gives you a warm fuzzy: I think you're safe to say you are saving 13.72%.
Lastly, if you want to know your retirement window, without MMM's curve. You have to dump the %'s and just do the straight math. Not the fun answer, but the only one I can figure out right now.