Comparative shopping engine Jellyfish.com has been acquired by Microsoft (NSDQ: MSFT), according to the company’s Live Search blog. The Madison-based company provides customers with a rebate on all of their purchases, by giving them a cut of the advertising revenue it receives.  Microsoft has expressed interest in this kind of model before, tossing around the idea of paying people who use Live Search. Microsoft sees Jellyfish bolstering the commerce side of Live.com, although it’s still unclear how the site will actually be integrated. Jellyfish has one announced funding round of $5 million last October from Kegonsa Capital Partners and Clyde Street Investments. Terms of the purchase were undisclosed. Some more details on how Jellyfish works in this IDG story.