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 $114.77   5.462%   $121.0387   $121.04   $121.05   $121.00  
  Purchase #2 $250.39   8.332%   $271.2525   $271.25   $271.25   $271.30  
  Purchase #3 $187.81   6.840%   $200.6562   $200.66   $200.65   $200.70  
  Purchase #4 $17.56   11.519%   $19.5827   $19.58   $19.60   $19.60  
  Purchase #5 $194.58   12.491%   $218.885   $218.89   $218.90   $218.90  
  Purchase #6 $197.85   11.827%   $221.2497   $221.25   $221.25   $221.20  
  Purchase #7 $98.46   12.826%   $111.0885   $111.09   $111.10   $111.10  
  Purchase #8 $101.30   7.251%   $108.6453   $108.65   $108.65   $108.60  
  Purchase #9 $228.59   13.761%   $260.0463   $260.05   $260.05   $260.00  
  Purchase #10 $110.98   3.613%   $114.9897   $114.99   $115.00   $115.00  
  10 purchase totals = $1,502.29       $1,647.45   $1,647.50   $1,647.40  
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?