You may be charged customs duties and taxes for something purchased online because duties and taxes are not included in the price of the goods you purchase and not included in the overall shipping costs.
Depend on Customs rule in your country you will pay duties & taxes.
When goods are not shipped domestically within a European Union, you are liable to pay any inbound duties & taxes which your local customs authority deems appropriate.
Shipment with low value in all most situation not stopped on custom (low value depend on you Customs rule)