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 $13.59   5.805%   $14.3789   $14.38   $14.40   $14.40  
  Purchase #2 $120.83   6.797%   $129.0428   $129.04   $129.05   $129.00  
  Purchase #3 $248.40   5.735%   $262.6457   $262.65   $262.65   $262.60  
  Purchase #4 $142.52   10.391%   $157.3293   $157.33   $157.35   $157.30  
  Purchase #5 $182.88   12.332%   $205.4328   $205.43   $205.45   $205.40  
  Purchase #6 $124.72   8.672%   $135.5357   $135.54   $135.55   $135.50  
  Purchase #7 $87.29   5.535%   $92.1215   $92.12   $92.10   $92.10  
  Purchase #8 $28.31   4.734%   $29.6502   $29.65   $29.65   $29.70  
  Purchase #9 $112.98   9.365%   $123.5606   $123.56   $123.55   $123.60  
  Purchase #10 $109.44   7.204%   $117.3241   $117.32   $117.30   $117.30  
  10 purchase totals = $1,170.96       $1,267.0216   $1,267.02   $1,267.05   $1,266.90  
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?