U.S. nickels (5 cent coins) are non-magnetic -- a blend of copper and nickel, and the same is true of dimes and quarters. Canadian coins of the same denominations are pure nickel and stick to a magnet. So, the presence of nickel in an alloy is not a predictor of the alloy's magnetic properties.
Also, there are indeed stainless steel alloys (containing iron and nickel) that are non-magnetic, as well as several that ARE magnetic.
When metals are alloyed the properties of the "parent" metals are not necessarily in evidence.