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 $57.54   3.558%   $59.5873   $59.59   $59.60   $59.60  
  Purchase #2 $176.74   10.761%   $195.759   $195.76   $195.75   $195.80  
  Purchase #3 $124.56   5.688%   $131.645   $131.65   $131.65   $131.60  
  Purchase #4 $121.49   13.708%   $138.1438   $138.14   $138.15   $138.10  
  Purchase #5 $84.31   13.522%   $95.7104   $95.71   $95.70   $95.70  
  Purchase #6 $189.96   11.468%   $211.7446   $211.74   $211.75   $211.70  
  Purchase #7 $188.86   13.449%   $214.2598   $214.26   $214.25   $214.30  
  Purchase #8 $235.65   11.110%   $261.8307   $261.83   $261.85   $261.80  
  Purchase #9 $60.97   12.321%   $68.4821   $68.48   $68.50   $68.50  
  Purchase #10 $22.53   9.493%   $24.6688   $24.67   $24.65   $24.70  
  10 purchase totals = $1,262.61       $1,401.83   $1,401.85   $1,401.80  
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?