Roundy's, Pewaukee, Wis., said last week it has acquired two independent store chains, Mega Marts, Oak Creek, Wis., and Ultra Mart, Menomonee Falls, Wis. Mega Marts operates 17 Pick ' n Save stores, 16 in Wisconsin and one in Illinois. The company's decision to become a Roundy's subsidiary follows the death of its founder, David A. Ulrich, in September 1998. Ultra Mart operated seven stores, all in Wisconsin, under the Pick 'n Save banner. Roundy's said it expects the Ultra Mart deal to close by mid-January and the Mega Marts deal to close in first quarter 2000. Primarily a wholesaler, Roundy's currently owns and operates nine distribution centers and 23 supermarkets in Wisconsin, Ohio, Michigan, Indiana and Illinois.