Make an item with 5 or 15% CDR
Scaling CDR blues give 15% CDR. Runes are now the only source that give CDR that isn't a multiple of 10. (The mastery gives 5%, but also raises the cap by 5%, so it doesn't affect how close you are to the cap at all.)
If you get scaling CDR blues, you get stuck at 35% CDR, or buying 45% and having 5% get wasted.
Put in an item with 5% or 15% CDR, so that we can use scaling CDR blues without feeling wonky.