If ever a 5# increase seems too much & you don't have an appropriately-weighted dumbell, you can stay with the same ol' dumbell, but add an ankle-weight to your wrist.
Another method I once used (but which took more time setting-up at 1st) was to tie rope around the handles of each dumbell & make a "rope handle" on each as well. This made the main handle width more hefty & I could place an ankle-weight on the "rope-handle" for slight weight increases (it was like a kettle-bell but with the handle heavier, or, when I placed the ankle-weight onto the dumbell & grabbed the rope, then I truly had a poor-man's kettle-bell).
If ever you can afford around 300-bucks, Nautilus makes a great adjustable-weight dumbell-set that adjusts in 2.5-lb increments up to 15#, & 5-lb increments for the most-part thereafter -- & the adjustments at each end of a dumbell need not be the same (can be "off-set"). Each dumbell goes up to just over 50-lbs fully-plated (& each handle alone is 5-lbs). It saves room... the adjustments are quick & easy... the only draw-back is that each dumbell is a bit bulky (on the long-side).