I don't know. Most other providers of mapping data hark on this point, though, that the Tiger data isn't accurate enough. Most I've seen give a resolution of 5-10 meters. For US data, the ADOL data is more accurate (8 meters). Plus pretty cheap too, $10 a zip code. License agreement doesn't seem too restrictive for the purposes here.

Here is a sample map for Concord, NH

Actually, now that I think about it, $10 a ZIP can add up unless you just want to focus on one area. For example, in the Bay Area I can easily see 40 ZIPs...