Let’s get directly to how you can introduce the coin payment system for your business. Most of the cryptocurrency payment gateway services offer API integration. The list of several services which allow you to do this:
Stripe - offers bitcoin payment integration via API, charges 0.8% per transaction.
Bitpay - receive Bitcoin payments by means of API integration, plugins for shopping carts and sample code libraries for Node and PHP.
Cryptonator - an online cryptocurrency wallet, supports 11 cryptocurrencies, takes 0.9% of processing fee, to receive digital money payments, to active such functionality, register a merchant account.
Coinpayments - integrated payment gateway, supports 105+ cryptocurrencies, offers API integration and plugins for such shopping carts, like WooCommerce, Opencart, Prestashop, Magento. Etc.
Coingate , another cryptocurrency payment gateway, draws 1% of fee, offers integration via API, e-commerce platforms plugins, and with their own Bitcoin POS mobile apps.