A bit out of my depth on this one so please bear with. We are having an issue when it comes to Magento (184.108.40.206) and PayPal Express conflicting the way they workout UK VAT rates in the checkout process.
An item which is £39.99 (inc-VAT) is inputted to Magento as £33.325 (ex-VAT). To get the £39.99 price Magento simply multiplies £33.325 by 1.2. PayPal however, receives the price of £33.325 and then rounds up to £33.33 as the ex-VAT price. It then multiplies by 1.2 giving the amount of £39.996, which it then in turn rounds up to £40.00.
In the checkout process PayPal is then flagging as error code 10426 "Item total is invalid." Are there any working solutions for this issue around? The issue is isolated to those prices with 3 decimal places ending in a 5. All other prices work correctly.