Вы можете сделать что-то вроде:
import pandas as pd
sample_grouped = pd.DataFrame({'location': ["NUEVO LEON", "ESTADO DE MEXICO", "TAMAULIPAS", "VERACRUZ", "DISTRITO FEDERAL", "COAHUILA", "JALISCO", "BAJA CALIFORNIA", "MICHOACAN", "GUANAJUATO"],
'amount': [9.566025, 8.979984, 7.939926, 7.686035, 7.257108, 5.283328, 4.835284, 4.280905, 4.160830, 4.129765]})
top_5 = sample_grouped[:5]
others = sample_grouped[5:]
others_total = others.iloc[:,[1]].sum()[0]
result = pd.DataFrame.append(top_5, pd.DataFrame({'location': ['OTHERS'], 'amount': [others_total]}))