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 $112.58   6.232%   $119.596   $119.60   $119.60   $119.60  
  Purchase #2 $169.84   3.623%   $175.9933   $175.99   $176.00   $176.00  
  Purchase #3 $20.98   3.362%   $21.6853   $21.69   $21.70   $21.70  
  Purchase #4 $245.66   5.807%   $259.9255   $259.93   $259.95   $259.90  
  Purchase #5 $54.71   4.280%   $57.0516   $57.05   $57.05   $57.10  
  Purchase #6 $179.47   12.778%   $202.4027   $202.40   $202.40   $202.40  
  Purchase #7 $223.52   6.440%   $237.9147   $237.91   $237.90   $237.90  
  Purchase #8 $121.72   12.142%   $136.4992   $136.50   $136.50   $136.50  
  Purchase #9 $152.82   6.246%   $162.3651   $162.37   $162.35   $162.40  
  Purchase #10 $100.50   7.237%   $107.7732   $107.77   $107.75   $107.80  
  10 purchase totals = $1,381.80       $1,481.2066   $1,481.21   $1,481.20   $1,481.30  
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?