I’m not getting your point …if your price includes tax and u check the option suggested by @revant_one the net_price is 90,9 (100 tax 10% included) …or, if you prefer: price = 110 => 100 net price + 10% tax.
If you need, you can uncheck the flag and in that case: price = net price… so if you have price = 1000, tax = 10% …your final price will be 1100 …
I’m not sure you’re doing the right thing …in erpnext u can create Sales Taxes and Charges Template for each tax and you will get shown tax amount for each template
In that case you would have to do reverse calculation. It would be 10/80 = 12.5% for both line items.
Say both rates are different eg. first row is 5% and the other as 10% then you would have to enter 5/85 = 5.882353% for line one and 10/85 = 11.764706% for the other.
You can create templates based on same and repeating invoice amount workings. This is also just a workaround to get things going on the system.