Is it wise to store total values into the SQL database?

I wanted to ask if it is a good idea to store total values into SQL database. By total values I mean stuff like total cost of an order, or the total quantity.

As an example, I'll have a table called orders which will have information like when it was created, who made the order and etc. Orders will relate to the table order_items which will hold the id of the item in the order, the quantity of the item in the order and the price at which it was sold (not the item`s original price).

In this situation, should I calculate the total cost of the order once and store it in the orders table, or should I calculate it every time I retrieve the order with the corresponding items?