Squeeling is sometimes cause by pads and/or rotors being glazed due to riding the brakes. Do you ride the brakes?
I don't recommend you do this... but I will tell you about it anyway...
If they're glazed, but the rotors are still in good shape and aren't discolored or have hot spots on them, you can probably "refinish" the rotors and replace the pads and fix the problem. In high school we used to do a kinda half-assed repair, but it worked 90% of the time. We'd make 4-5 scratches in the rotor, from the center to the edge with a screw driver or an awl or something that can scratch the rotor fairly easily. Then smeared some vavle lapping compound on the rotor and took it out and drove it around for a while, using the brakes... the valve lapping compound is abrasive enough to remove the glaze, yet not so abrasive that it gouges the rotor and reduces braking efficiency. Of course this is not a common way to fix squeeling brakes... but it's a cheap fix. Oh, and make sure when you bring the car back after the squeeling is gone you clean the rotors with brake clean before you put new pads on. And I highly recommend NOT using those pads from Auto Zone with the lifetime warranty cause it's such a hard, abrasive pad material that it chews up your rotors, which are much more expensive and time consuming to replace.