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 $84.43   12.473%   $94.961   $94.96   $94.95   $95.00  
  Purchase #2 $220.78   10.742%   $244.4962   $244.50   $244.50   $244.50  
  Purchase #3 $52.47   5.309%   $55.2556   $55.26   $55.25   $55.30  
  Purchase #4 $155.61   10.422%   $171.8277   $171.83   $171.85   $171.80  
  Purchase #5 $104.47   9.719%   $114.6234   $114.62   $114.60   $114.60  
  Purchase #6 $38.74   9.142%   $42.2816   $42.28   $42.30   $42.30  
  Purchase #7 $174.95   5.594%   $184.7367   $184.74   $184.75   $184.70  
  7 purchase totals = $831.45       $908.1822   $908.19   $908.20   $908.20