Let's do some math ..  Rounding examples of 8 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $94.67   10.153%   $104.2818   $104.28   $104.30   $104.30  
  Purchase #2 $213.90   13.231%   $242.2011   $242.20   $242.20   $242.20  
  Purchase #3 $181.72   7.108%   $194.6367   $194.64   $194.65   $194.60  
  Purchase #4 $91.47   6.640%   $97.5436   $97.54   $97.55   $97.50  
  Purchase #5 $38.31   12.306%   $43.0244   $43.02   $43.00   $43.00  
  Purchase #6 $181.89   9.609%   $199.3678   $199.37   $199.35   $199.40  
  Purchase #7 $71.35   6.397%   $75.9143   $75.91   $75.90   $75.90  
  Purchase #8 $46.92   11.310%   $52.2267   $52.23   $52.25   $52.20  
  8 purchase totals = $920.23       $1,009.1964   $1,009.19   $1,009.20   $1,009.10  
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?