You must be in another country if they charge you 
for duties tax, but from what I know (unless they 
changed their policies within the last week), the 
US does not charge any customs tax.

Now, as for customs opening your package, I would 
not be surprised for cels as since they are made 
with PAINT, some paint can exert certain fumes and 
as percaution, they don't want any packages with 
deadly chemicals in them.  So don't be too worried 
about that.

I sell many items on the internet (have an 
internet company) and recently, there are more 
customers complainging about their packages being 
held and opened by customs since it is getting 
closer to 9/11 and the post offices have received 
warnings to check all incoming packages 
thoroughly.  Just MAKE SURE YOU INSURE ALL 
PACKAGES!

J-Decker