Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $84.90   10.683%   $93.9699   $93.97   $93.95   $94.00  
  Purchase #2 $154.58   4.780%   $161.9689   $161.97   $161.95   $162.00  
  Purchase #3 $60.36   13.514%   $68.5171   $68.52   $68.50   $68.50  
  Purchase #4 $113.40   3.389%   $117.2431   $117.24   $117.25   $117.20  
  Purchase #5 $107.49   3.843%   $111.6208   $111.62   $111.60   $111.60  
  Purchase #6 $33.41   8.307%   $36.1854   $36.19   $36.20   $36.20  
  Purchase #7 $162.86   9.189%   $177.8252   $177.83   $177.85   $177.80  
  7 purchase totals = $717.00       $767.3304   $767.34   $767.30   $767.30