Shares of auto parts retailer AutoZone  (AZO) were up slightly Tuesday despite reporting mixed third quarter earnings. The Memphis-based company reported first quarter earnings of $9.36 a share, topping analysts expectations for the period by a nickel. Revenue of $2.47 billion missed analysts $2.5 billion expectations however. The company's top and bottom line results were ahead of the same period last year. During the quarter, AutoZone opened 16 new stores in the U.S. and five stores in Mexico.