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 $60.50   5.165%   $63.6248   $63.62   $63.60   $63.60  
  Purchase #2 $205.69   4.378%   $214.6951   $214.70   $214.70   $214.70  
  Purchase #3 $190.78   4.854%   $200.0405   $200.04   $200.05   $200.00  
  Purchase #4 $201.69   8.540%   $218.9143   $218.91   $218.90   $218.90  
  Purchase #5 $140.98   11.517%   $157.2167   $157.22   $157.20   $157.20  
  Purchase #6 $22.79   6.707%   $24.3185   $24.32   $24.30   $24.30  
  Purchase #7 $168.87   10.504%   $186.6081   $186.61   $186.60   $186.60  
  7 purchase totals = $991.30       $1,065.4180   $1,065.42   $1,065.35   $1,065.30