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 $219.26   3.829%   $227.6555   $227.66   $227.65   $227.70  
  Purchase #2 $239.48   12.731%   $269.9682   $269.97   $269.95   $270.00  
  Purchase #3 $23.53   6.797%   $25.1293   $25.13   $25.15   $25.10  
  Purchase #4 $239.89   3.821%   $249.0562   $249.06   $249.05   $249.10  
  Purchase #5 $106.84   12.379%   $120.0657   $120.07   $120.05   $120.10  
  Purchase #6 $96.72   13.276%   $109.5605   $109.56   $109.55   $109.60  
  Purchase #7 $220.80   12.409%   $248.1991   $248.20   $248.20   $248.20  
  Purchase #8 $149.68   12.356%   $168.1745   $168.17   $168.15   $168.20  
  Purchase #9 $65.74   13.512%   $74.6228   $74.62   $74.60   $74.60  
  Purchase #10 $119.58   12.823%   $134.9137   $134.91   $134.90   $134.90  
  10 purchase totals = $1,481.52       $1,627.3455   $1,627.35   $1,627.25   $1,627.50  
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?