How do I change a number axis to intervals?

I have to prepare a visual where I can show the state of open tickets and their age. I've been able to achieve this by creating a calculated field to calculate the age for an open ticket.

where [Date] is the date of creation of the ticket and '# of Days Open' indicated the age of the ticket.

The visualization comes out to be:

The problem for me is that I don't want to see so many bars. How can I convert the horizontal axis to intervals of 5? So tickets with age from 1-5 are stacked together, similarly for 6-10,11-15 and so on.

Thanks in advance.