While creating sales invoice gst is not calculated properly for different items

I am creating item with different Tax but while creating a sales invoice for all the items the tax is same
for example :-
4 items are created and all these 4 items are given different taxes ex :- item1 = 5% , item2= 18%, item3 = 8%, item4 = 10% and when we create a sales invoice all these items are given 9% taxes.