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 $200.96   3.546%   $208.086   $208.09   $208.10   $208.10  
  Purchase #2 $108.83   5.696%   $115.029   $115.03   $115.05   $115.00  
  Purchase #3 $73.79   10.255%   $81.3572   $81.36   $81.35   $81.40  
  Purchase #4 $157.66   11.626%   $175.9896   $175.99   $176.00   $176.00  
  Purchase #5 $87.41   5.179%   $91.937   $91.94   $91.95   $91.90  
  Purchase #6 $30.53   6.325%   $32.461   $32.46   $32.45   $32.50  
  Purchase #7 $52.61   3.730%   $54.5724   $54.57   $54.55   $54.60  
  7 purchase totals = $711.79       $759.4322   $759.44   $759.45   $759.50