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 $243.50   10.133%   $268.1739   $268.17   $268.15   $268.20  
  Purchase #2 $194.90   7.866%   $210.2308   $210.23   $210.25   $210.20  
  Purchase #3 $154.70   4.260%   $161.2902   $161.29   $161.30   $161.30  
  Purchase #4 $219.54   10.162%   $241.8497   $241.85   $241.85   $241.80  
  Purchase #5 $196.98   8.118%   $212.9708   $212.97   $212.95   $213.00  
  Purchase #6 $85.29   4.534%   $89.157   $89.16   $89.15   $89.20  
  Purchase #7 $141.27   6.359%   $150.2534   $150.25   $150.25   $150.30  
  Purchase #8 $209.64   9.810%   $230.2057   $230.21   $230.20   $230.20  
  Purchase #9 $72.32   8.353%   $78.3609   $78.36   $78.35   $78.40  
  Purchase #10 $236.52   5.813%   $250.2689   $250.27   $250.25   $250.30  
  10 purchase totals = $1,754.66       $1,892.7613   $1,892.76   $1,892.70   $1,892.90  
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?