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 $83.29   13.134%   $94.2293   $94.23   $94.25   $94.20  
  Purchase #2 $197.98   10.489%   $218.7461   $218.75   $218.75   $218.70  
  Purchase #3 $224.25   10.706%   $248.2582   $248.26   $248.25   $248.30  
  Purchase #4 $162.74   5.324%   $171.4043   $171.40   $171.40   $171.40  
  Purchase #5 $86.60   8.791%   $94.213   $94.21   $94.20   $94.20  
  Purchase #6 $105.78   10.249%   $116.6214   $116.62   $116.60   $116.60  
  Purchase #7 $18.69   10.690%   $20.688   $20.69   $20.70   $20.70  
  7 purchase totals = $879.33       $964.1603   $964.16   $964.15   $964.10