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 $92.81   7.861%   $100.1058   $100.11   $100.10   $100.10  
  Purchase #2 $46.56   12.204%   $52.2422   $52.24   $52.25   $52.20  
  Purchase #3 $52.99   4.564%   $55.4085   $55.41   $55.40   $55.40  
  Purchase #4 $232.96   7.602%   $250.6696   $250.67   $250.65   $250.70  
  Purchase #5 $190.50   5.531%   $201.0366   $201.04   $201.05   $201.00  
  Purchase #6 $214.59   7.124%   $229.8774   $229.88   $229.90   $229.90  
  Purchase #7 $113.48   4.120%   $118.1554   $118.16   $118.15   $118.20  
  Purchase #8 $192.38   6.791%   $205.4445   $205.44   $205.45   $205.40  
  Purchase #9 $143.27   12.741%   $161.524   $161.52   $161.50   $161.50  
  Purchase #10 $136.87   3.467%   $141.6153   $141.62   $141.60   $141.60  
  10 purchase totals = $1,416.41       $1,516.09   $1,516.05   $1,516.00  
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?