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 $207.38   5.574%   $218.9394   $218.94   $218.95   $218.90  
  Purchase #2 $131.58   10.547%   $145.4577   $145.46   $145.45   $145.50  
  Purchase #3 $140.81   12.377%   $158.2381   $158.24   $158.25   $158.20  
  Purchase #4 $99.79   13.400%   $113.1619   $113.16   $113.15   $113.20  
  Purchase #5 $167.42   8.309%   $181.3309   $181.33   $181.35   $181.30  
  Purchase #6 $45.61   10.362%   $50.3361   $50.34   $50.35   $50.30  
  Purchase #7 $75.30   6.843%   $80.4528   $80.45   $80.45   $80.50  
  Purchase #8 $214.81   12.265%   $241.1564   $241.16   $241.15   $241.20  
  Purchase #9 $136.67   6.349%   $145.3472   $145.35   $145.35   $145.30  
  Purchase #10 $155.35   4.482%   $162.3128   $162.31   $162.30   $162.30  
  10 purchase totals = $1,374.72       $1,496.7333   $1,496.74   $1,496.75   $1,496.70  
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?