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 $48.56   6.804%   $51.864   $51.86   $51.85   $51.90  
  Purchase #2 $43.92   13.466%   $49.8343   $49.83   $49.85   $49.80  
  Purchase #3 $129.71   11.468%   $144.5851   $144.59   $144.60   $144.60  
  Purchase #4 $76.95   3.418%   $79.5802   $79.58   $79.60   $79.60  
  Purchase #5 $40.87   9.613%   $44.7988   $44.80   $44.80   $44.80  
  Purchase #6 $230.44   12.596%   $259.4662   $259.47   $259.45   $259.50  
  Purchase #7 $58.79   11.224%   $65.3886   $65.39   $65.40   $65.40  
  Purchase #8 $113.46   12.428%   $127.5608   $127.56   $127.55   $127.60  
  Purchase #9 $84.31   8.466%   $91.4477   $91.45   $91.45   $91.40  
  Purchase #10 $18.44   7.507%   $19.8243   $19.82   $19.80   $19.80  
  10 purchase totals = $845.45       $934.3500   $934.35   $934.35   $934.40  
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?