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 $87.28   10.497%   $96.4418   $96.44   $96.45   $96.40  
  Purchase #2 $164.37   4.422%   $171.6384   $171.64   $171.65   $171.60  
  Purchase #3 $216.73   8.650%   $235.4771   $235.48   $235.50   $235.50  
  Purchase #4 $30.44   13.237%   $34.4693   $34.47   $34.45   $34.50  
  Purchase #5 $244.91   8.637%   $266.0629   $266.06   $266.05   $266.10  
  Purchase #6 $220.82   5.370%   $232.678   $232.68   $232.70   $232.70  
  Purchase #7 $168.44   7.184%   $180.5407   $180.54   $180.55   $180.50  
  Purchase #8 $151.55   8.372%   $164.2378   $164.24   $164.25   $164.20  
  Purchase #9 $117.90   10.742%   $130.5648   $130.56   $130.55   $130.60  
  Purchase #10 $85.94   8.370%   $93.1332   $93.13   $93.15   $93.10  
  10 purchase totals = $1,488.38       $1,605.24   $1,605.30   $1,605.20  
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?