Go to Administration -> Configuration -> Currencies. Find your currency and click edit. On the edit page you will see Custom Formatting field. In it enter something like 0.00 руб.
Thank you for your trying to help. But that does not help. The problem is that it saves it like "руб" removing a dot from the end, which is not good. So, I filled just like you wrote — "0.00 руб.". For example the price was "1300,00 р.", after formatting it becomes "1300.00 руб". I need it to be 0.00 руб.