Many thanks to the Teachingnest Blog for this great reference.
Number sliders can be a great way for students to share rounding of numbers, also in developing numbers that meet a certain criteria, as well as playing games with one another.
We often play games in the classroom where I ask students to find a two digit number that is a multiple say of 5 and three, with a sum of 6, and with a difference of 4. In this way the students are hearing and using the vocabulary necessary for classroom discourse in mathematics. I also sometimes create a number given that the number is less than 70 but greater than 10, to again use additional vocabulary and restraints on the number. Also multiple answers are then available giving time to the students who need additional time and adding excitement to those who have the pattern.