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 $114.66   9.422%   $125.4633   $125.46   $125.45   $125.50  
  Purchase #2 $51.62   9.767%   $56.6617   $56.66   $56.65   $56.70  
  Purchase #3 $221.29   5.436%   $233.3193   $233.32   $233.30   $233.30  
  Purchase #4 $246.38   5.414%   $259.719   $259.72   $259.70   $259.70  
  Purchase #5 $144.81   11.477%   $161.4298   $161.43   $161.45   $161.40  
  Purchase #6 $15.31   4.863%   $16.0545   $16.05   $16.05   $16.10  
  Purchase #7 $13.87   7.362%   $14.8911   $14.89   $14.90   $14.90  
  7 purchase totals = $807.94       $867.5387   $867.53   $867.50   $867.60