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 $61.38   7.302%   $65.862   $65.86   $65.85   $65.90  
  Purchase #2 $189.76   5.190%   $199.6085   $199.61   $199.60   $199.60  
  Purchase #3 $233.63   13.424%   $264.9925   $264.99   $265.00   $265.00  
  Purchase #4 $161.73   8.208%   $175.0048   $175.00   $175.00   $175.00  
  Purchase #5 $76.29   8.482%   $82.7609   $82.76   $82.75   $82.80  
  Purchase #6 $219.63   8.863%   $239.0958   $239.10   $239.10   $239.10  
  Purchase #7 $138.86   8.403%   $150.5284   $150.53   $150.55   $150.50  
  Purchase #8 $10.56   6.813%   $11.2795   $11.28   $11.30   $11.30  
  Purchase #9 $230.55   3.777%   $239.2579   $239.26   $239.25   $239.30  
  Purchase #10 $137.29   6.837%   $146.6765   $146.68   $146.70   $146.70  
  10 purchase totals = $1,459.68       $1,575.0668   $1,575.07   $1,575.10   $1,575.20  
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?