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 $104.61   10.675%   $115.7771   $115.78   $115.80   $115.80  
  Purchase #2 $91.43   7.549%   $98.3321   $98.33   $98.35   $98.30  
  Purchase #3 $216.56   6.689%   $231.0457   $231.05   $231.05   $231.00  
  Purchase #4 $73.58   10.818%   $81.5399   $81.54   $81.55   $81.50  
  Purchase #5 $236.71   10.489%   $261.5385   $261.54   $261.55   $261.50  
  Purchase #6 $220.77   9.195%   $241.0698   $241.07   $241.05   $241.10  
  Purchase #7 $191.48   4.475%   $200.0487   $200.05   $200.05   $200.00  
  Purchase #8 $36.52   12.214%   $40.9806   $40.98   $41.00   $41.00  
  Purchase #9 $139.72   9.696%   $153.2673   $153.27   $153.25   $153.30  
  Purchase #10 $213.57   12.431%   $240.1189   $240.12   $240.10   $240.10  
  10 purchase totals = $1,524.95       $1,663.73   $1,663.75   $1,663.60  
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?