Changing the currency precision (or rounding up) the amount in subtotal (in POS or Sales)

I want to round up or down the subtotal amount (for example, 299.98 to 300 and 97.50 to 98; see the image below) per order line. I think I can do this in the Customize Form and change the currency precision, but I cannot found the correct field to customize. I cannot found the field corresponding to the subtotal “Amount.” (Note: I only want to round off the subtotal amount.)

I discovered the solution. Go to Customize Form and select POS Invoice Item. Go to number 33 Amount, edit and change the precision to 0.