Technically God just wants us to give back...so I would say by the technical rule it's "ok" However if your a member of a local church by doing this your punishing them. Churches have bills to, and from my experience churches often run in the red-meaning they don't have enough money to fully cover all their needs.
And honestly if one is just looking to give the 10% suggested by the Bible, that's kinda Missing the point. One should give like the poor woman in the temple who only gave 2 mites...and I don't mean you should give everything, what I mean is you should give with your heart, whether it's 2% or 20%. Personally I do give a 10% tithe to the church as a base...and then I go from there. If there's a shoe ministry I give in addition to that 10% if there's a missions trip I give extra straight to it. I also donate to various other entities that need money.
My point isn't to say look at me. My point is, everyone is different, everyones finances are different, but you should never forsake the fellowship, and you should always give with your heart. If your not sure how, how much, or who to give to, pray for God's guidance, and be willing to listen for the answer.