Ok, based on marginal tax rates, if the taxman is taking a "third of what I make", the author needs to be making $600,000 per year!!! Poor "down home" guy making all that green!
Incidently, "Jesus" doesn't see a single cent of a tithe given to a church. It goes to administrative costs, community and poverty outreach, building maintenance (I guess if the building is an extension of Jesus, that might count), etc. While Christians are certainly encouraged to be generous with what they have, the idea of a 10% tithe is pretty contentious and not really universally held.
Jesus loved the poor and hated the rich and moneylenders. He encouraged people to give to Caesar that which is Caesar's.
So, is "10% Good Enough for Jesus"? I doubt it. Frankly, assuming there is a Jesus sitting in judgment of the song's author, I don't see him being impressed by the attitude.