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 $105.51   5.592%   $111.4101   $111.41   $111.40   $111.40  
  Purchase #2 $240.37   7.207%   $257.6935   $257.69   $257.70   $257.70  
  Purchase #3 $68.83   6.676%   $73.4251   $73.43   $73.45   $73.40  
  Purchase #4 $207.98   5.865%   $220.178   $220.18   $220.20   $220.20  
  Purchase #5 $142.81   10.430%   $157.7051   $157.71   $157.70   $157.70  
  Purchase #6 $248.93   10.407%   $274.8361   $274.84   $274.85   $274.80  
  Purchase #7 $102.94   4.113%   $107.1739   $107.17   $107.15   $107.20  
  Purchase #8 $119.94   11.561%   $133.8063   $133.81   $133.80   $133.80  
  Purchase #9 $162.78   10.378%   $179.6733   $179.67   $179.65   $179.70  
  Purchase #10 $165.37   3.105%   $170.5047   $170.50   $170.50   $170.50  
  10 purchase totals = $1,565.46       $1,686.4061   $1,686.41   $1,686.40   $1,686.40  
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?