Know anything about removing dents in a fender using a Dolly and Hammer? The same idea applies to the rim. Put something hard and shaped somewhat like the inside of the rim, and tap --I said, TAP, not hammer-- until it is smooth again. It won't come out perfect, but if you're careful, it can be fairly close.
Remember, though, that the wheel will never be as strong as it was before you mangled it.
But, if you are going to continue jumping, you would be doing yourself and your family a favor by investing in some wheels that are made for that kind of abuse. It may save you a trip to the hospital.
Also, if yu ever move on to something a little better than the x-Mart special, You can transfer the the same good wheels.