Let's do some math ..  Rounding examples of 10 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $44.75   9.403%   $48.9578   $48.96   $48.95   $49.00  
  Purchase #2 $144.40   3.550%   $149.5262   $149.53   $149.55   $149.50  
  Purchase #3 $117.74   13.427%   $133.5489   $133.55   $133.55   $133.50  
  Purchase #4 $204.89   6.121%   $217.4313   $217.43   $217.45   $217.40  
  Purchase #5 $65.94   9.166%   $71.9841   $71.98   $72.00   $72.00  
  Purchase #6 $178.99   4.684%   $187.3739   $187.37   $187.35   $187.40  
  Purchase #7 $200.81   7.200%   $215.2683   $215.27   $215.25   $215.30  
  Purchase #8 $217.77   6.635%   $232.219   $232.22   $232.20   $232.20  
  Purchase #9 $229.96   13.705%   $261.476   $261.48   $261.50   $261.50  
  Purchase #10 $183.45   4.553%   $191.8025   $191.80   $191.80   $191.80  
  10 purchase totals = $1,588.70       $1,709.59   $1,709.60   $1,709.60  
Come on folks.. this just does not make any cents. We got rid of the 1/2 cent back in 1857.. Getting rid of the 1 cent coin is way, WAY past due. The penny has become a social and cultural anachronism. If our friends in Canada, Australia and a dozen other countries can stop the use of their pennies, why can't we?