No doubt it will be different on different computers, Luckygirl, but I click on the three horizontal lines in the top right hand corner of my screen (customize and control Google Chrome), choose History from the dropdown, check that Cookies are ticked, click on Clear Browsing Data, choose the timescale (usually from the past hour), Clear Browsing Data again, and your cookies and the record of your what you've been looking at (mainly GN) from the last hour mysteriously disappear.
I have to do this before I go to any website via Topcashback, otherwise they don't always recognise that I've gone in via their site and don't award me the dosh.
The disadvantage is that some of your stored passwords, including for GN, seem to disappear and you have to type them in again. I'm sure some clever clogs will be able to tell us how to stop this happening.
Thanks for the cookie clearing tip, Leticia.