How is this done without the use of List?
Just
If[StringPart[#, -1] == ".", # <> "0%", # <> "%"] & @ ToString @ Round[100*#[[2]], 0.1]
but consider:
ToString[NumberForm[100 #[[2]], {Infinity, 1}]] <> "%" & /@
{{, 0.0156}, {, 0.01}}
{"1.6%", "1.0%"}
Or
TextString@Quantity[Round[100 #[[2]], .1], "Percent"] & /@
{{, 0.0156}, {, 0.01}}