The Oklahoma Tax Commission can charge it do to the way the law is wrote. Something about how state funds can not be used to pay for processing fees. I will see if I can find it but here is the Oklahoma law regarding surcharges.
I figured there was some sort of annoying loophole in there for them. Kind of like how I paid about $1000 less for my jet ski that I just had registered than what they taxed me on. Even though I have a bill of sale showing exactly how much I paid for it, they taxed me on what the state thinks I should have paid for it.
I've complained enough, I'll stop hijacking this thread now. :-)