Halloween is shaping up as more of a treat than a trick for retailers this year. Despite haunting sales last season, the National Retail Federation is predicting a major comeback in 2010.Total Halloween spending is expected to reach about $5.8 billion, according to the federation. The average shopper likely will spend about $66.28, up from last year’s $56.31 and on par with the $66.54 from 2008.