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 $13.51   4.463%   $14.113   $14.11   $14.10   $14.10  
  Purchase #2 $157.89   4.293%   $164.6682   $164.67   $164.65   $164.70  
  Purchase #3 $65.33   11.557%   $72.8802   $72.88   $72.90   $72.90  
  Purchase #4 $139.46   3.653%   $144.5545   $144.55   $144.55   $144.60  
  Purchase #5 $164.67   4.668%   $172.3568   $172.36   $172.35   $172.40  
  Purchase #6 $140.36   11.172%   $156.041   $156.04   $156.05   $156.00  
  Purchase #7 $128.63   10.814%   $142.54   $142.54   $142.55   $142.50  
  Purchase #8 $189.56   9.745%   $208.0326   $208.03   $208.05   $208.00  
  Purchase #9 $196.92   10.360%   $217.3209   $217.32   $217.30   $217.30  
  Purchase #10 $158.52   10.239%   $174.7509   $174.75   $174.75   $174.80  
  10 purchase totals = $1,354.85       $1,467.2581   $1,467.25   $1,467.25   $1,467.30  
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?