It's not "ども" but " どうも " and it can be used to greet or thank people. ごはんをわけてくれてどうもありがとう。You can even use it just like that to give your appreciation. どうも、きょうはなににいたしますか？　It's usually used between co-workers, customer-employee (usually they know each other very well) as well as employee-employer( or other people in higher social status ) It's very flexible to use. Good Luck!!