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 $90.70   3.461%   $93.8391   $93.84   $93.85   $93.80  
  Purchase #2 $61.78   4.861%   $64.7831   $64.78   $64.80   $64.80  
  Purchase #3 $85.36   9.580%   $93.5375   $93.54   $93.55   $93.50  
  Purchase #4 $84.45   8.582%   $91.6975   $91.70   $91.70   $91.70  
  Purchase #5 $76.94   11.596%   $85.862   $85.86   $85.85   $85.90  
  Purchase #6 $245.28   3.501%   $253.8673   $253.87   $253.85   $253.90  
  Purchase #7 $224.54   7.275%   $240.8753   $240.88   $240.90   $240.90  
  Purchase #8 $140.63   9.315%   $153.7297   $153.73   $153.75   $153.70  
  Purchase #9 $143.85   7.167%   $154.1597   $154.16   $154.15   $154.20  
  Purchase #10 $116.46   8.689%   $126.5792   $126.58   $126.60   $126.60  
  10 purchase totals = $1,269.99       $1,358.9304   $1,358.94   $1,359.00   $1,359.00  
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?