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 $79.81   6.602%   $85.0791   $85.08   $85.10   $85.10  
  Purchase #2 $102.92   5.691%   $108.7772   $108.78   $108.80   $108.80  
  Purchase #3 $102.45   9.269%   $111.9461   $111.95   $111.95   $111.90  
  Purchase #4 $74.37   5.597%   $78.5325   $78.53   $78.55   $78.50  
  Purchase #5 $117.34   5.872%   $124.2302   $124.23   $124.25   $124.20  
  Purchase #6 $51.45   3.217%   $53.1051   $53.11   $53.10   $53.10  
  Purchase #7 $39.42   7.266%   $42.2843   $42.28   $42.30   $42.30  
  Purchase #8 $107.25   8.848%   $116.7395   $116.74   $116.75   $116.70  
  Purchase #9 $161.88   3.618%   $167.7368   $167.74   $167.75   $167.70  
  Purchase #10 $169.88   11.833%   $189.9819   $189.98   $190.00   $190.00  
  10 purchase totals = $1,006.77       $1,078.4127   $1,078.42   $1,078.55   $1,078.30  
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?