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 $207.83   9.637%   $227.8586   $227.86   $227.85   $227.90  
  Purchase #2 $127.61   5.134%   $134.1615   $134.16   $134.15   $134.20  
  Purchase #3 $206.61   9.857%   $226.9755   $226.98   $227.00   $227.00  
  Purchase #4 $32.63   7.325%   $35.0201   $35.02   $35.00   $35.00  
  Purchase #5 $216.43   12.124%   $242.67   $242.67   $242.65   $242.70  
  Purchase #6 $215.79   11.645%   $240.9187   $240.92   $240.90   $240.90  
  Purchase #7 $196.32   10.684%   $217.2948   $217.29   $217.30   $217.30  
  7 purchase totals = $1,203.22       $1,324.8992   $1,324.90   $1,324.85   $1,325.00