I have been working at McDicks, oh sorry, I mean McDonalds, for over 8 months.
And even I know, they don't give raises. The only raise you get is when you've been promoted to either Crew Trainer, or some sort of Manager. If you ask for a raise, I can almost guarantee it will be a no. I know someone who's been working there for 3 years and who hasn't gotten a raise yet. In fact, I bet any manager my Head Manager would laugh in the cashier's face if he/she asked for a raise. It's a joke to them, because it's only a fast-food job. It's practically worthless.
Though, from my understanding, they are allowed to give you a raise after a certain amount of time. Which I don't know exactly. So, you can ask for the raise, but there's not much of a chance you will get it if they haven't already offered it. Like other person stated, get a new job. The only time I saw someone at my work get offered more than minimum was when he announced he was leaving to work at Subways because they offered him 10$ an hour (minimum here is 9.65). They offered him more, but DIDN'T even match it. So he still left.
In my opinion, look for a new job. McDonalds experience is like a jackpot for employers. There is no minimum-wage job as demanding as working at McDonalds, so it looks all nice and pretty on the application. You can get a job almost anywhere (customer service) with over a year experience at McDs. I suggest you look for a job with a higher pay! That's if they say no, of course, for your raise. At least ask, there's not really much that can happen other than a Yes or a No.