You can use the mobile payment feature of the TD Bank app to make a purchase. To make a payment at a merchant's checkout counter, open the TD Bank app, tap the "Pay Now" link, choose the card you’d like to pay from and tap the “Pay” button. Once a timer is active, hold the back of your phone over the payment terminal. Then, you can get the receipt from the cashier.
If you want to skip the step of launching the app and selecting the card, you can enable the “Always On” option. Doing so will enable you to pay through the TD Bank app from the default card, without having to launch the app.