Here in Brazil they put at least some packages through an x-ray, so if you say they're books and there's something else in there as well then they'll notice, open the package, and then either tax you for whatever is on the invoice or on the product tags.
If it's a ludicrous value on the invoice (let's say you declared Diesel jeans for $10 for example) and there are no tags, they'll do a "research" for the product's price, which means they'll guess it, and being customs officers they'll likely aim high.
Your best bet is using a proxy service (www.nybox.com is great), shipping your stuff to them, and then having it mailed to you. They even offer the service of producing an additional invoice for your package, so you can lower the declared value of the goods. This can save a lot of money, but remember to pick reasonable values. They won't know the brand of what you're packing through the invoice usually, so you can declare jeans for, say $40. They'll only open the package if they have reason to be suspicious, and that's when they'll notice the brand, if it's famous.
Declaring it as a gift has pretty much zero effect here.
There's also a chance your package won't get taxed at all, just because they receive too many packages daily at customs.
Notice this is all my experience, which is probably similar to other customs in other countries, but not exactly the same.
So basically you can't dodge the customs fees completely, but you can lower them by declaring a lower value on shipment, one is that is not ludicrous, though.
