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 $89.27   8.590%   $96.9383   $96.94   $96.95   $96.90  
  Purchase #2 $19.56   11.203%   $21.7513   $21.75   $21.75   $21.80  
  Purchase #3 $54.47   12.509%   $61.2837   $61.28   $61.30   $61.30  
  Purchase #4 $192.81   11.109%   $214.2293   $214.23   $214.25   $214.20  
  Purchase #5 $125.43   7.186%   $134.4434   $134.44   $134.45   $134.40  
  Purchase #6 $21.43   11.840%   $23.9673   $23.97   $23.95   $24.00  
  Purchase #7 $197.97   5.821%   $209.4938   $209.49   $209.50   $209.50  
  7 purchase totals = $700.94       $762.1071   $762.10   $762.15   $762.10