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 $195.74   6.391%   $208.2497   $208.25   $208.25   $208.20  
  Purchase #2 $195.76   9.703%   $214.7546   $214.75   $214.75   $214.80  
  Purchase #3 $80.28   8.583%   $87.1704   $87.17   $87.15   $87.20  
  Purchase #4 $166.33   3.377%   $171.947   $171.95   $171.95   $171.90  
  Purchase #5 $48.50   13.795%   $55.1906   $55.19   $55.20   $55.20  
  Purchase #6 $242.95   13.555%   $275.8819   $275.88   $275.90   $275.90  
  Purchase #7 $139.25   13.241%   $157.6881   $157.69   $157.70   $157.70  
  7 purchase totals = $1,068.81       $1,170.8823   $1,170.88   $1,170.90   $1,170.90