[{"_id":ObjectId("5a934e000102030405000000"),amount:122434},{"_id":ObjectId("5a934e000102030405000001"),amount:122434.5},{"_id":ObjectId("5a934e000102030405000002"),amount:122434.1},{"_id":ObjectId("5a934e000102030405000003"),amount:-122434.0000001}]

db.collection.aggregate([{$match:{$expr:{$lte:[{$abs:{$subtract:["$amount",{$round:"$amount"}]}},0.000001]}}}])