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 $60.85   13.306%   $68.9467   $68.95   $68.95   $68.90  
  Purchase #2 $142.63   8.335%   $154.5182   $154.52   $154.50   $154.50  
  Purchase #3 $232.53   3.650%   $241.0173   $241.02   $241.00   $241.00  
  Purchase #4 $17.94   8.376%   $19.4427   $19.44   $19.45   $19.40  
  Purchase #5 $194.39   9.805%   $213.4499   $213.45   $213.45   $213.40  
  Purchase #6 $63.73   8.161%   $68.931   $68.93   $68.95   $68.90  
  Purchase #7 $45.39   7.165%   $48.6422   $48.64   $48.65   $48.60  
  7 purchase totals = $757.46       $814.9480   $814.95   $814.95   $814.70