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 $195.49   9.534%   $214.128   $214.13   $214.15   $214.10  
  Purchase #2 $104.46   11.621%   $116.5993   $116.60   $116.60   $116.60  
  Purchase #3 $39.93   10.416%   $44.0891   $44.09   $44.10   $44.10  
  Purchase #4 $69.74   3.472%   $72.1614   $72.16   $72.15   $72.20  
  Purchase #5 $198.96   3.572%   $206.0669   $206.07   $206.05   $206.10  
  Purchase #6 $155.64   4.337%   $162.3901   $162.39   $162.40   $162.40  
  Purchase #7 $132.79   5.342%   $139.8836   $139.88   $139.90   $139.90  
  7 purchase totals = $897.01       $955.3184   $955.32   $955.35   $955.40