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 $74.51   8.245%   $80.6533   $80.65   $80.65   $80.70  
  Purchase #2 $38.72   13.788%   $44.0587   $44.06   $44.05   $44.10  
  Purchase #3 $209.64   11.104%   $232.9184   $232.92   $232.90   $232.90  
  Purchase #4 $196.30   10.316%   $216.5503   $216.55   $216.55   $216.60  
  Purchase #5 $238.65   7.421%   $256.3602   $256.36   $256.35   $256.40  
  Purchase #6 $28.51   7.623%   $30.6833   $30.68   $30.70   $30.70  
  Purchase #7 $23.77   8.176%   $25.7134   $25.71   $25.70   $25.70  
  Purchase #8 $66.76   9.781%   $73.2898   $73.29   $73.30   $73.30  
  Purchase #9 $121.34   9.846%   $133.2871   $133.29   $133.30   $133.30  
  Purchase #10 $97.83   7.383%   $105.0528   $105.05   $105.05   $105.10  
  10 purchase totals = $1,096.03       $1,198.5673   $1,198.56   $1,198.55   $1,198.80  
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?