Using strokes in groups of five was not easy, either, because I always kept thinking I missed one or two, so I'd re-count, yet again.
I finally came up with a method that works for me, and maybe it will work for you.
I'm sure every long-time, experienced knitter/crocheter already does this, but since I only just figured it out, thought I'd share with those of us who didn't already know.
Mark every so many rows, at the outside edge, with a wee scrap of different colored yarn, something that stands out in the piece you are working on (light on dark, dark on light, etc.), and attach it like a piece of fringe. Just pull a loop through, and pull the ends through the loop. It is easily detached later.
For my scarf, I found that 23 rows equal 1 foot. Because I want them between 3 and 4 feet long, I ended up putting a single "fringe" piece every 23 rows. All I had to do was glance at the edge of my scarf every so often, and count, 1 foot, 2 feet, etc.
You could easily mark every 10 rows, or every 30 rows, whatever works with the piece you are making.