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 $182.58   8.266%   $197.6721   $197.67   $197.65   $197.70  
  Purchase #2 $81.72   11.829%   $91.3867   $91.39   $91.40   $91.40  
  Purchase #3 $32.47   4.548%   $33.9467   $33.95   $33.95   $33.90  
  Purchase #4 $206.98   3.265%   $213.7379   $213.74   $213.75   $213.70  
  Purchase #5 $149.48   5.384%   $157.528   $157.53   $157.55   $157.50  
  Purchase #6 $119.35   8.369%   $129.3384   $129.34   $129.35   $129.30  
  Purchase #7 $250.54   4.261%   $261.2155   $261.22   $261.20   $261.20  
  7 purchase totals = $1,023.12       $1,084.8253   $1,084.84   $1,084.85   $1,084.70