Ok. Here's another query. Did I port it correctly? Thanks.
Oracle
SELECT t.* into taxes
FROM ec_orders o, ec_addresses a, ec_sales_tax_by_state t
WHERE o.shipping_address=a.address_id
AND a.usps_abbrev=t.usps_abbrev(+)
AND o.order_id=v_order_id;
PostgreSQL
SELECT into taxes t.*
FROM ec_orders o
JOIN
ec_addresses on (o.shipping_address=a.address_id)
LEFT JOIN
ec_sales_tax_by_state t using (usps_abbrev)
WHERE o.order_id=v_order_id;