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 $87.48   10.405%   $96.5823   $96.58   $96.60   $96.60  
  Purchase #2 $207.67   8.481%   $225.2825   $225.28   $225.30   $225.30  
  Purchase #3 $61.29   5.106%   $64.4195   $64.42   $64.40   $64.40  
  Purchase #4 $37.46   3.726%   $38.8558   $38.86   $38.85   $38.90  
  Purchase #5 $212.49   7.156%   $227.6958   $227.70   $227.70   $227.70  
  Purchase #6 $152.63   3.216%   $157.5386   $157.54   $157.55   $157.50  
  Purchase #7 $143.89   6.335%   $153.0054   $153.01   $153.00   $153.00  
  7 purchase totals = $902.91       $963.3799   $963.39   $963.40   $963.40