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 $55.96   9.581%   $61.3215   $61.32   $61.30   $61.30  
  Purchase #2 $36.66   13.710%   $41.6861   $41.69   $41.70   $41.70  
  Purchase #3 $143.70   7.137%   $153.9559   $153.96   $153.95   $154.00  
  Purchase #4 $48.69   13.727%   $55.3737   $55.37   $55.35   $55.40  
  Purchase #5 $5.96   10.638%   $6.594   $6.59   $6.60   $6.60  
  Purchase #6 $89.92   9.410%   $98.3815   $98.38   $98.40   $98.40  
  Purchase #7 $10.68   12.700%   $12.0364   $12.04   $12.05   $12.00  
  Purchase #8 $238.39   11.278%   $265.2756   $265.28   $265.30   $265.30  
  Purchase #9 $18.69   6.836%   $19.9676   $19.97   $19.95   $20.00  
  Purchase #10 $68.73   7.158%   $73.6497   $73.65   $73.65   $73.60  
  10 purchase totals = $717.38       $788.25   $788.25   $788.30  
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?