Shares of CarMax (KMX 5.18%) rallied as much as 13% early Thursday, then settled to close up 5.2% after the used-vehicle retailer announced better-than-expected quarterly earnings. CarMax also resumed its share repurchase program.CarMax's soaring profitabilityOn one hand, for its fiscal third quarter ended Nov. 30, Carmax's revenue declined 5.5% year over year to $6.15 billion, technically missing analysts' consensus estimates for sales of $6.3 billion. On the other hand, CarMax's net earnings more than dou ...