JSFiddle - React, Tailwind, and code Playground

JavaScript

const roundOrNil = (n) => Math.abs(~~n - n) > 0.1 ? null : ~~n;

console.log(roundOrNil(7)); // 7
console.log(roundOrNil(7.3)); // null
console.log(roundOrNil(-5.2)); // null
console.log(roundOrNil(-5.9)); // null
console.log(roundOrNil(-5.1)); // -5
console.log(roundOrNil(-5.05)); // -5