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 $211.91   6.555%   $225.8007   $225.80   $225.80   $225.80  
  Purchase #2 $44.52   9.236%   $48.6319   $48.63   $48.65   $48.60  
  Purchase #3 $189.65   7.148%   $203.2062   $203.21   $203.20   $203.20  
  Purchase #4 $155.29   13.728%   $176.6082   $176.61   $176.60   $176.60  
  Purchase #5 $177.41   9.268%   $193.8524   $193.85   $193.85   $193.90  
  Purchase #6 $46.58   5.657%   $49.215   $49.22   $49.20   $49.20  
  Purchase #7 $136.72   5.209%   $143.8417   $143.84   $143.85   $143.80  
  Purchase #8 $70.93   8.430%   $76.9094   $76.91   $76.90   $76.90  
  Purchase #9 $59.67   11.376%   $66.4581   $66.46   $66.45   $66.50  
  Purchase #10 $96.50   5.741%   $102.0401   $102.04   $102.05   $102.00  
  10 purchase totals = $1,189.18       $1,286.5637   $1,286.57   $1,286.55   $1,286.50  
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?