Ok, so yeah, that's the problem. The WC object in code is only returning the total price without tax, so it's getting entered as 135.00 instead of 162.00.
That's one of the quirky things that keeps changing in WC. One version will send us the pricing with tax included, and then the next version won't, and then the next version will again. It's been very annoying.
Essentially we're just going to have add all sorts of checks and balances to get this working.
Another option would be to disable the line items from getting passed to PayPal. Then the PayPal transaction details wouldn't have the line item break down, but it would have the WC order #, and you could find the item details in that order, of course.
If you want to give that a shot open up the file at /paypal-for-woocommerce/classes/wc-gateway-paypal-express-angelleye.php
Go to line 1360 and you'll see the following.
$Payment['order_items'] = $PaymentOrderItems;
Comment that line out. Also, at line 1366 you'll see...
$Payment['itemamt'] = $total_items+$total_discount;
Go ahead and comment that line out as well. Upload that change and run a test to see if the problem goes away.