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 $153.52   11.360%   $170.9599   $170.96   $170.95   $171.00  
  Purchase #2 $118.81   12.417%   $133.5626   $133.56   $133.55   $133.60  
  Purchase #3 $83.30   12.502%   $93.7142   $93.71   $93.70   $93.70  
  Purchase #4 $17.37   8.815%   $18.9012   $18.90   $18.90   $18.90  
  Purchase #5 $232.36   9.394%   $254.1879   $254.19   $254.20   $254.20  
  Purchase #6 $184.68   9.853%   $202.8765   $202.88   $202.90   $202.90  
  Purchase #7 $202.34   7.233%   $216.9753   $216.98   $217.00   $217.00  
  Purchase #8 $37.97   6.415%   $40.4058   $40.41   $40.40   $40.40  
  Purchase #9 $134.69   13.795%   $153.2705   $153.27   $153.25   $153.30  
  Purchase #10 $149.97   7.859%   $161.7561   $161.76   $161.75   $161.80  
  10 purchase totals = $1,315.01       $1,446.6100   $1,446.62   $1,446.60   $1,446.80  
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?