In 2016, the USA increased the minimum threshold for customs duties from $200 to $800, which means most goods valued below $800 are not subject to duties or taxes.
If the package has duties applied, it is your customer who is responsible for paying customs duties (or import taxes) on the items shipped from China across the US border. Make sure you add such information on your store so that your customers are aware that the items they ordered may come from abroad so they should expect to pay customs duties. The point of being upfront is to protect you from complaints or refund requests because of customs costs.