Yes, this is indeed possible. The formula function READRES will download the feed data as a text value containing the XML. You can use text manipulation functions such as SEARCH to find the data your want.

This is very tricky, though. From tonight, 2.6 b612, there are two new functions which can be used instead in combination with READRES:
REPLACEREGEX - does a regular expression search and replace, allowing back-references
XPATH - evaluates an XPath expression against an XML document.
You can use either - in this case, XPATH is easier. Try the attached IOK file in 2.6 b612 or later to see the two new functions in use with this currency data.