I'm having the same problem!
Checked everything mentioned above, still all prices are displayed excluding TAX
Edit:
When, in front office, I change the language to English, TAX is included.....
When I change it back to Dutch, TAX is excluded again.
Edit2:
Only In root prices are excl. TAX.
When a product is opened or quick-viewed, prices are including TAX
Also, it's category, prices are correctly shown including TAX.
Only on HOME, there's no TAX
What's this????