Picking spare inner tube size
In case of inner tube, difference between 1.90 and 1.95 is totally negligible. The tubes will be completely interchangeable.

Rather than carrying a few spare tubes on your bike at all times, experienced riders most often carry only one spare tube + patch kit. It takes less space and weighs less than multiple spare tubes. It's rare to catch more than 1 flat on a single ride, and if you do, patching a tube takes only a few minutes.