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 $43.30   6.202%   $45.9855   $45.99   $46.00   $46.00  
  Purchase #2 $244.65   6.695%   $261.0293   $261.03   $261.05   $261.00  
  Purchase #3 $152.48   5.863%   $161.4199   $161.42   $161.40   $161.40  
  Purchase #4 $49.26   3.585%   $51.026   $51.03   $51.05   $51.00  
  Purchase #5 $65.35   6.313%   $69.4755   $69.48   $69.50   $69.50  
  Purchase #6 $184.76   3.147%   $190.5744   $190.57   $190.55   $190.60  
  Purchase #7 $96.54   6.628%   $102.9387   $102.94   $102.95   $102.90  
  7 purchase totals = $836.34       $882.4493   $882.46   $882.50   $882.40