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 $62.48   9.763%   $68.5799   $68.58   $68.60   $68.60  
  Purchase #2 $192.98   12.291%   $216.6992   $216.70   $216.70   $216.70  
  Purchase #3 $164.94   11.358%   $183.6739   $183.67   $183.65   $183.70  
  Purchase #4 $40.49   9.621%   $44.3855   $44.39   $44.40   $44.40  
  Purchase #5 $128.67   8.315%   $139.3689   $139.37   $139.35   $139.40  
  Purchase #6 $104.81   9.225%   $114.4787   $114.48   $114.50   $114.50  
  Purchase #7 $164.28   9.615%   $180.0755   $180.08   $180.10   $180.10  
  7 purchase totals = $858.65       $947.2616   $947.27   $947.30   $947.40