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 $107.40   9.191%   $117.2711   $117.27   $117.25   $117.30  
  Purchase #2 $197.87   9.388%   $216.446   $216.45   $216.45   $216.40  
  Purchase #3 $63.27   7.582%   $68.0671   $68.07   $68.05   $68.10  
  Purchase #4 $242.33   11.866%   $271.0849   $271.08   $271.10   $271.10  
  Purchase #5 $244.82   11.839%   $273.8042   $273.80   $273.80   $273.80  
  Purchase #6 $100.29   8.602%   $108.9169   $108.92   $108.90   $108.90  
  Purchase #7 $241.25   5.184%   $253.7564   $253.76   $253.75   $253.80  
  Purchase #8 $110.38   7.611%   $118.781   $118.78   $118.80   $118.80  
  Purchase #9 $235.70   4.516%   $246.3442   $246.34   $246.35   $246.30  
  Purchase #10 $71.45   11.455%   $79.6346   $79.63   $79.65   $79.60  
  10 purchase totals = $1,614.76       $1,754.10   $1,754.10   $1,754.10  
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?