[{items:[["Tax",10,20,30],["FX Adjustments",10,20,30],["Tax",10,20,30],["FX Adjustments",10,20,30]]}]

db.collection.aggregate([{$unwind:"$items"},{$group:{_id:{$arrayElemAt:["$items",0]},values:{$push:{$slice:["$items",1,{$size:"$items"}]}}}},{$project:{_id:1,values:{$map:{input:{$range:[0,{$size:{$arrayElemAt:["$values",0]}}]},as:"index",in:{$reduce:{input:"$values",initialValue:0,in:{$add:["$$value",{$arrayElemAt:["$$this","$$index"]}]}}}}}}},{$group:{_id:null,items:{$push:{$concatArrays:[["$_id"],"$values"]}}}}])