The last anser is an old wives tale and I find it surprising how many people believe it without thinking.
Test it for yourself, put a teaspoon of rice, a teaspoon and a teaspoon of wateri in salt in a cup, swirl around for a few seconds, You will find that the salt has absorbed the water and the rice is barely damp.
Rice is far less hyrgoscopic (able to absorb water) than salt. The only possible benefits would be : 1 to keep the rice dry, or 2 to use the rice grains break up the soggy salt when shaking the shaker.
Living on a boat, the only answer that I have found is to keep the salt in an airtight container (there are no cool dry places on a boat in the tropics)