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 $63.89   9.416%   $69.9059   $69.91   $69.90   $69.90  
  Purchase #2 $107.49   11.588%   $119.9459   $119.95   $119.95   $119.90  
  Purchase #3 $66.72   8.615%   $72.4679   $72.47   $72.45   $72.50  
  Purchase #4 $206.77   3.424%   $213.8498   $213.85   $213.85   $213.80  
  Purchase #5 $110.42   11.674%   $123.3104   $123.31   $123.30   $123.30  
  Purchase #6 $162.70   6.803%   $173.7685   $173.77   $173.75   $173.80  
  Purchase #7 $132.53   6.388%   $140.996   $141.00   $141.00   $141.00  
  Purchase #8 $211.89   11.519%   $236.2976   $236.30   $236.30   $236.30  
  Purchase #9 $223.87   5.555%   $236.306   $236.31   $236.30   $236.30  
  Purchase #10 $98.86   12.266%   $110.9862   $110.99   $111.00   $111.00  
  10 purchase totals = $1,385.14       $1,497.8342   $1,497.86   $1,497.80   $1,497.80  
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?