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 $63.52   8.639%   $69.0075   $69.01   $69.00   $69.00  
  Purchase #2 $100.61   5.412%   $106.055   $106.06   $106.05   $106.10  
  Purchase #3 $12.62   13.218%   $14.2881   $14.29   $14.30   $14.30  
  Purchase #4 $125.75   7.843%   $135.6126   $135.61   $135.60   $135.60  
  Purchase #5 $169.34   10.249%   $186.6957   $186.70   $186.70   $186.70  
  Purchase #6 $96.49   4.569%   $100.8986   $100.90   $100.90   $100.90  
  Purchase #7 $217.49   4.538%   $227.3597   $227.36   $227.35   $227.40  
  Purchase #8 $201.32   13.667%   $228.8344   $228.83   $228.85   $228.80  
  Purchase #9 $71.67   9.390%   $78.3998   $78.40   $78.40   $78.40  
  Purchase #10 $186.61   8.775%   $202.985   $202.99   $203.00   $203.00  
  10 purchase totals = $1,245.42       $1,350.1364   $1,350.15   $1,350.15   $1,350.20  
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?