Retailers that enjoyed robust sales during the 2010 holiday season should not expect a repeat performance, according to a forecast from the National Retail Federation (NRF). The Washington, D.C., trade organization predicted a 2.8% increase this year, totaling $465.6 billion. In 2010, holiday retail sales rose 5.2% over the previous year, according to the NRF. The 10-year average holiday sales increase is 2.6%.