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 $31.43   11.735%   $35.1183   $35.12   $35.10   $35.10  
  Purchase #2 $43.61   10.667%   $48.2619   $48.26   $48.25   $48.30  
  Purchase #3 $134.53   7.768%   $144.9803   $144.98   $145.00   $145.00  
  Purchase #4 $59.53   4.175%   $62.0154   $62.02   $62.00   $62.00  
  Purchase #5 $215.30   3.295%   $222.3941   $222.39   $222.40   $222.40  
  Purchase #6 $195.42   4.398%   $204.0146   $204.01   $204.00   $204.00  
  Purchase #7 $222.80   6.778%   $237.9014   $237.90   $237.90   $237.90  
  Purchase #8 $190.62   4.372%   $198.9539   $198.95   $198.95   $199.00  
  Purchase #9 $181.77   13.596%   $206.4834   $206.48   $206.50   $206.50  
  Purchase #10 $98.50   11.617%   $109.9427   $109.94   $109.95   $109.90  
  10 purchase totals = $1,373.51       $1,470.0660   $1,470.05   $1,470.05   $1,470.10  
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?