Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $135.70   7.744%   $146.2086   $146.21   $146.20   $146.20  
  Purchase #2 $194.67   10.856%   $215.8034   $215.80   $215.80   $215.80  
  Purchase #3 $39.88   12.276%   $44.7757   $44.78   $44.80   $44.80  
  Purchase #4 $33.73   6.392%   $35.886   $35.89   $35.90   $35.90  
  Purchase #5 $26.95   4.344%   $28.1207   $28.12   $28.10   $28.10  
  Purchase #6 $95.41   8.303%   $103.3319   $103.33   $103.35   $103.30  
  Purchase #7 $177.66   12.872%   $200.5284   $200.53   $200.55   $200.50  
  7 purchase totals = $704.00       $774.66   $774.70   $774.60  
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?