Как найти в объекте число и сравнить его

const $sum = { 
  "document":{ 
  "0.3":{"in_city":"1600","0_49":"2200","50_200":"3200","200_999":"4200"}, 
  "0.5":{"in_city":"2000","0_49":"2400","50_200":"3400","200_999":"4400"}, 
  "1":{"in_city":"2400","0_49":"2700","50_200":"3700","200_999":"4700"}, 
  "1.5":{"in_city":"2600","0_49":"3000","50_200":"4000","200_999":"5000"}, 
  "2":{"in_city":"2800","0_49":"3500","50_200":"4500","200_999":"5500"}, 
  "2.5":{"in_city":"3000","0_49":"3800","50_200":"4800","200_999":"5800"}, 
  "3":{"in_city":"3200","0_49":"4100","50_200":"5100","200_999":"6100"}, 
  "3.5":{"in_city":"3350","0_49":"4300","50_200":"5400","200_999":"6400"},                                         
  "4":{"in_city":"3550","0_49":"4700","50_200":"5700","200_999":"6700"}, 
  "4.5":{"in_city":"3750","0_49":"5000","50_200":"6000","200_999":"7000"}, 
  "5":{"in_city":"3950","0_49":"5300","50_200":"6300","200_999":"7300"} 
  }, 
} 
const num = 1.2; 
 
const item = Object.keys($sum.document).map(item => +item).sort().find(key => key > num); 
console.log($sum.document[item])

$sum = { 
"document":{ 
    "0.3":{"in_city":"1600","0_49":"2200","50_200":"3200","200_999":"4200"}, 
    "0.5":{"in_city":"2000","0_49":"2400","50_200":"3400","200_999":"4400"}, 
    "1":{"in_city":"2400","0_49":"2700","50_200":"3700","200_999":"4700"}, 
    "1.5":{"in_city":"2600","0_49":"3000","50_200":"4000","200_999":"5000"}, 
    "2":{"in_city":"2800","0_49":"3500","50_200":"4500","200_999":"5500"}, 
    "2.5":{"in_city":"3000","0_49":"3800","50_200":"4800","200_999":"5800"}, 
    "3":{"in_city":"3200","0_49":"4100","50_200":"5100","200_999":"6100"}, 
    "3.5":{"in_city":"3350","0_49":"4300","50_200":"5400","200_999":"6400"},                                         
    "4":{"in_city":"3550","0_49":"4700","50_200":"5700","200_999":"6700"}, 
    "4.5":{"in_city":"3750","0_49":"5000","50_200":"6000","200_999":"7000"}, 
    "5":{"in_city":"3950","0_49":"5300","50_200":"6300","200_999":"7300"} 
} 
}; 
$("#check").click(function(){ 
  let need=$("#need").val(); 
  //Сортируем ключи 
  let keys=Object.keys($sum.document).sort(function(a, b){ 
    return parseFloat(a) - parseFloat(b); 
  }); 
  //Ищем большее значение и выходим из цикла 
  for(let i in keys){ 
    if(need<keys[i]){ 
      console.log(keys[i]+":"+JSON.stringify($sum.document[keys[i]])); 
      break; 
    } 
  } 
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> 
<input type="text" id="need"> 
<button id="check">Получить ближайшеее значение</button>