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 $197.64   5.553%   $208.6149   $208.61   $208.60   $208.60  
  Purchase #2 $106.76   10.378%   $117.8396   $117.84   $117.85   $117.80  
  Purchase #3 $68.63   10.816%   $76.053   $76.05   $76.05   $76.10  
  Purchase #4 $157.31   8.344%   $170.4359   $170.44   $170.45   $170.40  
  Purchase #5 $241.40   12.806%   $272.3137   $272.31   $272.30   $272.30  
  Purchase #6 $182.63   5.225%   $192.1724   $192.17   $192.15   $192.20  
  Purchase #7 $111.62   3.463%   $115.4854   $115.49   $115.50   $115.50  
  7 purchase totals = $1,065.99       $1,152.9149   $1,152.91   $1,152.90   $1,152.90