For best results, you really need a truly flat washer like the shims that come with a dado set, though 1/16" would be a stack since the biggest shim I have is only 0.020" You can buy a 5/8" bore flat washer at places like Lowe's (or most any HW store) for under $1, but these are usually stamped so they would possibly have a slight ridge around the edges. The outer diameter needs to be the same as your current arbor washer that goes behind the arbor nut when installing a blade.
Alternatively, you can buy a "blade stabilizer" which will be flat and plenty thick enough, but they cost more.
