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 $188.26   3.459%   $194.7719   $194.77   $194.75   $194.80  
  Purchase #2 $132.61   11.790%   $148.2447   $148.24   $148.25   $148.20  
  Purchase #3 $60.51   13.703%   $68.8017   $68.80   $68.80   $68.80  
  Purchase #4 $218.25   8.793%   $237.4407   $237.44   $237.45   $237.40  
  Purchase #5 $41.39   4.219%   $43.1362   $43.14   $43.15   $43.10  
  Purchase #6 $30.55   5.398%   $32.1991   $32.20   $32.20   $32.20  
  Purchase #7 $167.66   9.761%   $184.0253   $184.03   $184.05   $184.00  
  Purchase #8 $102.81   12.573%   $115.7363   $115.74   $115.75   $115.70  
  Purchase #9 $215.64   4.508%   $225.3611   $225.36   $225.35   $225.40  
  Purchase #10 $166.31   3.363%   $171.903   $171.90   $171.90   $171.90  
  10 purchase totals = $1,323.99       $1,421.6200   $1,421.62   $1,421.65   $1,421.50  
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?