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 $16.86   11.312%   $18.7672   $18.77   $18.75   $18.80  
  Purchase #2 $101.36   10.674%   $112.1792   $112.18   $112.20   $112.20  
  Purchase #3 $178.29   6.554%   $189.9751   $189.98   $190.00   $190.00  
  Purchase #4 $36.94   10.432%   $40.7936   $40.79   $40.80   $40.80  
  Purchase #5 $69.82   5.868%   $73.917   $73.92   $73.90   $73.90  
  Purchase #6 $140.74   13.173%   $159.2797   $159.28   $159.30   $159.30  
  Purchase #7 $103.40   9.448%   $113.1692   $113.17   $113.15   $113.20  
  Purchase #8 $84.72   8.217%   $91.6814   $91.68   $91.70   $91.70  
  Purchase #9 $182.52   7.216%   $195.6906   $195.69   $195.70   $195.70  
  Purchase #10 $102.48   11.571%   $114.338   $114.34   $114.35   $114.30  
  10 purchase totals = $1,017.13       $1,109.7910   $1,109.80   $1,109.85   $1,109.90  
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?