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 $95.29   12.134%   $106.8525   $106.85   $106.85   $106.90  
  Purchase #2 $141.50   11.474%   $157.7357   $157.74   $157.75   $157.70  
  Purchase #3 $249.25   4.836%   $261.3037   $261.30   $261.30   $261.30  
  Purchase #4 $176.88   8.636%   $192.1554   $192.16   $192.15   $192.20  
  Purchase #5 $189.68   10.380%   $209.3688   $209.37   $209.35   $209.40  
  Purchase #6 $60.44   10.455%   $66.759   $66.76   $66.75   $66.80  
  Purchase #7 $136.95   12.138%   $153.573   $153.57   $153.55   $153.60  
  7 purchase totals = $1,049.99       $1,147.7481   $1,147.75   $1,147.70   $1,147.90