There will be up to two types of taxes which you might have to pay.
The first will be the Sales Tax pertaining to the United States of America (US). Certain States in the US are tax-free states and as a result no sales tax will be levied on the procured merchandises.
The second will be Goods and Services Tax (GST) in Singapore. GST reliefs are granted on imported items if the total value of the goods plus shipping costs does not exceed SG$400.
Where the value exceeds SG$400, the entire sum would be subjected to GST.
The current GST rate is 7%.