Dai is by design a very secure stable coin and equally so, a very secure payment method. All Dai transactions are completely transparent, hosted on a decentralized blockchain for an added layer of checks and balances.
Keep in mind, like all cryptos, once you make a transaction there is no going back. Unlike a credit card payment erroneously issued, you will not be able to claim back Dai if you sent it to the wrong merchant. For your financial protection, be careful in copying the address when sending funds, and the decimal points in the amount you enter.