Paypal IPN keeps failing - The totals of the cart item amounts do not match order amounts - paypal

Question

We are using Woocommerce and Woocommerce Subscriptions. For some reason by default, Woocommerce Subscriptions (Reference Transactions) do not pass or include the Tax amount to Paypal. So I ended up modifying the class files and added in the field "TAXAMT" in the IPN.
However, when I did so, it is now giving us the error:
[L_ERRORCODE0] => 10413
[L_ERRORCODE1] => 10004
[L_SHORTMESSAGE0] => Transaction refused because of an invalid argument. See additional error messages for details.
[L_SHORTMESSAGE1] => Invalid Data
[L_LONGMESSAGE0] => The totals of the cart item amounts do not match order amounts.
[L_LONGMESSAGE1] => This transaction cannot be processed.
[L_SEVERITYCODE0] => Error
[L_SEVERITYCODE1] => Error
Can anybody please help me identify what's missing or what is wrong here?
Below is the IPN request sent to paypal (via woocommerce paypal logs)
This is a recurring product. The product costs $7.70 and the Tax is $0.77 with a total of $8.47
[USER] => ****************
[PWD] => ****************
[SIGNATURE] => ********************************************************
[VERSION] => 124
[METHOD] => DoReferenceTransaction
[REFERENCEID] => B-4CR65046J0487452E
[BUTTONSOURCE] => WooThemes_Cart
[RETURNFMFDETAILS] => 1
[AMT] => 7.70
[CURRENCYCODE] => AUD
[INVNUM] => WC-5184
[PAYMENTACTION] => Sale
[NOTIFYURL] => https://affgo.co/go/wc-api/WC_Gateway_Paypal/
[CUSTOM] => {"order_id":5184,"order_key":"wc_order_56bad2660bf0f"}
[TAXAMT] => 0.77
[ITEMAMT] => 8.47
[L_PAYMENTREQUEST_0_NAME0] => Subscriptions → IMMag Monthly
[L_PAYMENTREQUEST_0_AMT0] => 7.70
[L_PAYMENTREQUEST_0_QTY0] => 1
[PAYMENTREQUEST_0_ITEMAMT] => 7.70
[PAYMENTREQUEST_0_SHIPPINGAMT] => 0.00
[PAYMENTREQUEST_0_TAXAMT] => 0.77