Thanks for the replies.
I've been reading some more on the topic, and while I'm about to give up and use a USB reader with a laptop instead, the possibility of using a Square Credit Card Reader as my card reader instead is very tantalizing.
Square makes a card reader that plugs into phones as a mic input, and then their software reads cards. I've plugged the reader into a mic input on my PC, and swiping a card generates a tangible waveform as an audio signature.. I feel like if I knew just a little bit more about what I'm doing, I'd be able to decode the audio and identify the dorm cards we're using.