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 $241.86   3.344%   $249.9478   $249.95   $249.95   $249.90  
  Purchase #2 $202.53   5.614%   $213.9   $213.90   $213.90   $213.90  
  Purchase #3 $164.57   7.129%   $176.3022   $176.30   $176.30   $176.30  
  Purchase #4 $50.26   11.628%   $56.1042   $56.10   $56.10   $56.10  
  Purchase #5 $160.70   12.327%   $180.5095   $180.51   $180.50   $180.50  
  Purchase #6 $16.53   8.411%   $17.9203   $17.92   $17.90   $17.90  
  Purchase #7 $113.82   6.455%   $121.1671   $121.17   $121.15   $121.20  
  Purchase #8 $131.74   10.703%   $145.8401   $145.84   $145.85   $145.80  
  Purchase #9 $229.48   10.200%   $252.887   $252.89   $252.90   $252.90  
  Purchase #10 $226.28   11.186%   $251.5917   $251.59   $251.60   $251.60  
  10 purchase totals = $1,537.77       $1,666.1699   $1,666.17   $1,666.15   $1,666.10  
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?