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 $87.58   8.599%   $95.111   $95.11   $95.10   $95.10  
  Purchase #2 $53.53   3.334%   $55.3147   $55.31   $55.30   $55.30  
  Purchase #3 $71.66   13.397%   $81.2603   $81.26   $81.25   $81.30  
  Purchase #4 $140.73   4.183%   $146.6167   $146.62   $146.60   $146.60  
  Purchase #5 $93.43   3.556%   $96.7524   $96.75   $96.75   $96.80  
  Purchase #6 $114.76   9.855%   $126.0696   $126.07   $126.05   $126.10  
  Purchase #7 $116.51   8.621%   $126.5543   $126.55   $126.55   $126.60  
  7 purchase totals = $678.20       $727.6790   $727.67   $727.60   $727.80