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 $153.41   5.716%   $162.1789   $162.18   $162.20   $162.20  
  Purchase #2 $94.73   11.255%   $105.3919   $105.39   $105.40   $105.40  
  Purchase #3 $119.82   8.192%   $129.6357   $129.64   $129.65   $129.60  
  Purchase #4 $229.45   12.370%   $257.833   $257.83   $257.85   $257.80  
  Purchase #5 $240.85   12.333%   $270.554   $270.55   $270.55   $270.60  
  Purchase #6 $33.44   9.495%   $36.6151   $36.62   $36.60   $36.60  
  Purchase #7 $67.68   4.212%   $70.5307   $70.53   $70.55   $70.50  
  Purchase #8 $155.47   4.117%   $161.8707   $161.87   $161.85   $161.90  
  Purchase #9 $113.91   3.777%   $118.2124   $118.21   $118.20   $118.20  
  Purchase #10 $43.66   10.390%   $48.1963   $48.20   $48.20   $48.20  
  10 purchase totals = $1,252.42       $1,361.0187   $1,361.02   $1,361.05   $1,361.00  
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?