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 $179.42   5.142%   $188.6458   $188.65   $188.65   $188.60  
  Purchase #2 $61.83   12.274%   $69.419   $69.42   $69.40   $69.40  
  Purchase #3 $111.41   5.229%   $117.2356   $117.24   $117.25   $117.20  
  Purchase #4 $88.60   12.253%   $99.4562   $99.46   $99.45   $99.50  
  Purchase #5 $87.32   6.501%   $92.9967   $93.00   $93.00   $93.00  
  Purchase #6 $174.39   4.862%   $182.8688   $182.87   $182.85   $182.90  
  Purchase #7 $118.71   5.549%   $125.2972   $125.30   $125.30   $125.30  
  Purchase #8 $62.89   9.228%   $68.6935   $68.69   $68.70   $68.70  
  Purchase #9 $159.54   3.472%   $165.0792   $165.08   $165.10   $165.10  
  Purchase #10 $196.31   9.430%   $214.822   $214.82   $214.80   $214.80  
  10 purchase totals = $1,240.42       $1,324.5140   $1,324.53   $1,324.50   $1,324.50  
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?