If you make ladder attenuators e.g. R-2R ladder for ~6dB steps, there is another pair of integers which gives nice attenuation steps: R-75R. (you could use e.g. 15R and R/5 since that can be more convenient, or 5R and R/15 if that suits you better.) The steps you get are even closer to 1dB than the R-2R steps are to 6dB. You need a funny value on the last stage to terminate it, but at least there is only one of those (or two if you need to terminate both ends for some reason).
Chris