My wife and I both come from a small town in the south, and I asked both of her parents for permission. I suppose I could've asked for their blessing instead, but the wording didn't bother me and I knew that they'd say yes (we'd been dating for almost 8 years).
I didn't look at it as a requirement from the "right way to do things" perspective. It's a chance to talk with her parents about how they feel. It also lets them know that you value their opinion, even if you feel that the answer won't matter in the end. Some parents may also feel that they are expected to pay for all or a majority of the wedding expenses. Asking allows them to feel like they're still in control of the their money, even though they'll probably say yes.
As far as worrying about getting told no, don't think about it because it probably won't happen. If it does, simply ask why not. This is another reason to do it in front of both parents, the mother will almost always say yes immediately unless she hates you, helping to persuade the father
In the end, you really don't have anything to lose by asking. Be it either permission or blessing. If he says no when you ask then he would've said no when he found out later. And if he says yes, then you have taken the romantic route for your girlfriend and the "traditional" route for your future inlaws.