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 $213.98   6.415%   $227.7068   $227.71   $227.70   $227.70  
  Purchase #2 $120.93   10.128%   $133.1778   $133.18   $133.20   $133.20  
  Purchase #3 $10.30   10.756%   $11.4079   $11.41   $11.40   $11.40  
  Purchase #4 $199.62   3.296%   $206.1995   $206.20   $206.20   $206.20  
  Purchase #5 $196.44   12.238%   $220.4803   $220.48   $220.50   $220.50  
  Purchase #6 $13.94   4.810%   $14.6105   $14.61   $14.60   $14.60  
  Purchase #7 $107.56   3.569%   $111.3988   $111.40   $111.40   $111.40  
  7 purchase totals = $862.77       $924.9816   $924.99   $925.00   $925.00