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 $10.47   7.506%   $11.2559   $11.26   $11.25   $11.30  
  Purchase #2 $165.89   7.849%   $178.9107   $178.91   $178.90   $178.90  
  Purchase #3 $124.25   13.564%   $141.1033   $141.10   $141.10   $141.10  
  Purchase #4 $188.86   12.789%   $213.0133   $213.01   $213.00   $213.00  
  Purchase #5 $217.71   5.412%   $229.4925   $229.49   $229.50   $229.50  
  Purchase #6 $240.98   3.283%   $248.8914   $248.89   $248.90   $248.90  
  Purchase #7 $190.79   5.372%   $201.0392   $201.04   $201.05   $201.00  
  Purchase #8 $145.67   9.736%   $159.8524   $159.85   $159.85   $159.90  
  Purchase #9 $91.30   6.242%   $96.9989   $97.00   $97.00   $97.00  
  Purchase #10 $16.91   11.142%   $18.7941   $18.79   $18.80   $18.80  
  10 purchase totals = $1,392.83       $1,499.34   $1,499.35   $1,499.40  
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?