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 $236.82   11.305%   $263.5925   $263.59   $263.60   $263.60  
  Purchase #2 $154.52   6.522%   $164.5978   $164.60   $164.60   $164.60  
  Purchase #3 $62.34   10.167%   $68.6781   $68.68   $68.70   $68.70  
  Purchase #4 $26.97   3.475%   $27.9072   $27.91   $27.90   $27.90  
  Purchase #5 $37.71   13.700%   $42.8763   $42.88   $42.90   $42.90  
  Purchase #6 $6.44   4.591%   $6.7357   $6.74   $6.75   $6.70  
  Purchase #7 $17.42   7.227%   $18.6789   $18.68   $18.70   $18.70  
  Purchase #8 $172.47   12.272%   $193.6355   $193.64   $193.65   $193.60  
  Purchase #9 $30.59   9.601%   $33.5269   $33.53   $33.55   $33.50  
  Purchase #10 $149.60   6.749%   $159.6965   $159.70   $159.70   $159.70  
  10 purchase totals = $894.88       $979.9254   $979.95   $980.05   $979.90  
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?