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 $190.99   7.713%   $205.7211   $205.72   $205.70   $205.70  
  Purchase #2 $138.82   10.264%   $153.0685   $153.07   $153.05   $153.10  
  Purchase #3 $105.37   8.636%   $114.4698   $114.47   $114.45   $114.50  
  Purchase #4 $87.67   5.589%   $92.5699   $92.57   $92.55   $92.60  
  Purchase #5 $232.36   11.335%   $258.698   $258.70   $258.70   $258.70  
  Purchase #6 $141.35   3.508%   $146.3086   $146.31   $146.30   $146.30  
  Purchase #7 $87.26   9.727%   $95.7478   $95.75   $95.75   $95.70  
  Purchase #8 $159.80   10.477%   $176.5422   $176.54   $176.55   $176.50  
  Purchase #9 $70.72   5.389%   $74.5311   $74.53   $74.55   $74.50  
  Purchase #10 $233.93   6.288%   $248.6395   $248.64   $248.65   $248.60  
  10 purchase totals = $1,448.27       $1,566.2965   $1,566.30   $1,566.25   $1,566.20  
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?