Coupon causes TAX_TOTAL_MISMATCH (333)

[AlexP11223]

In some cases when a coupon is being used, the customer get error, TAX_TOTAL_MISMATCH.

POST https://api.paypal.com/v2/checkout/orders
Request Body: {"intent":"CAPTURE","purchase_units":[{"reference_id":"default","amount":{"currency_code":"USD","value":"80.16","breakdown":{"item_total":{"currency_code":"USD","value":"95.00"},"shipping":{"currency_code":"USD","value":"0.00"},"tax_total":{"currency_code":"USD","value":"6.54"},"discount":{"currency_code":"USD","value":"21.38"}}},"description":"","items":[{"name":"prod2","unit_amount":{"currency_code":"USD","value":"95.00"},"quantity":1,"description":"","sku":"","category":"PHYSICAL_GOODS","tax":{"currency_code":"USD","value":"6.53"}}],"payee":{"merchant_id":"9LJB9AXR9TPMU"},"shipping":{"name":{"full_name":"John Doe"},"address":{"country_code":"US","address_line_1":"1 Main St","address_line_2":"1","admin_area_1":"MN","admin_area_2":"ny","postal_code":"99501"}}}],"application_context":{"user_action":"CONTINUE","shipping_preference":"GET_FROM_FILE","landing_page":"LOGIN","locale":"en-US","brand_name":"\"WooCommerce PayPal Payments\"","return_url":"http:\/\/wc-pp.myhost\/?wc-ajax=ppc-return-url","cancel_url":"http:\/\/wc-pp.myhost\/checkout\/"},"payer":{"name":{"given_name":"John","surname":"Doe"},"email_address":"[email protected]","address":{"country_code":"US","address_line_1":"1 Main St","address_line_2":"1","admin_area_1":"MN","admin_area_2":"ny","postal_code":"99501"},"phone":{"phone_type":"HOME","phone_number":{"national_number":"4088381528"}}},"payment_method":{"payee_preferred":"UNRESTRICTED","payer_selected":"PAYPAL"}}
Response Debug ID: e999372fa047d
Response: Array
(
    [code] => 422
    [message] => Unprocessable Entity
)

Response Body: {"name":"UNPROCESSABLE_ENTITY","details":[{"field":"/purchase_units/@reference_id=='default'/amount/breakdown/tax_total/value","value":"6.54","issue":"TAX_TOTAL_MISMATCH","description":"Should equal sum of (tax * quantity) across all items for a given purchase_unit"}],"message":"The requested action could not be performed, semantically incorrect, or failed business validation.","debug_id":"e999372fa047d","links":[{"href":"https://developer.paypal.com/docs/api/orders/v2/#error-TAX_TOTAL_MISMATCH","rel":"information_link","method":"GET"}]}

Steps to reproduce

It seems like it is reproduced only in some environments.

I reproduced it in the docker env with WC 5.8, PHP 7.1.

Add a product with price $95, add tax 6.8750%, and $20 coupon.

Go to checkout, enter the coupon, pay, and this error will appear:

[ajakeward]

Hi, is there any workarounds on this? We have an issue with our Black Friday sale now.

[Dinamiko]

Hello @ajakeward,

The fix (#373) is tested and merged into trunk so it will be included in the next release (1.6.3), in the meantime I´m attaching the plugin package from trunk in case you want to use it:
woocommerce-paypal-payments.zip