I'm majoring in CIS but am very interested in neuroscience. I am therefore planning on minoring in cognitive science and/or biology. My question: how much chemistry should I take? A term? A year? Keep in mind I must be conservative with my credits.

Minimal chemistry courses to take are introductory chemistry classes and organic chemistry. More chemistry in the neural sciences is never bad. But, I'd say that's the minimum.

in addition to organic chemistry, you should include biochemistry. Electrochemistry and physical chemistry are good to know too.