[{customer:"A",job:"Apple",chemical:{name:"Chem A",quantity:500}},{customer:"A",job:"Banana",chemical:{name:"Chem B",quantity:400}},{customer:"A",job:"Banana",chemical:{name:"Chem C",quantity:300}},{customer:"B",job:"Cherry",chemical:{name:"Chem A",quantity:200}}]

db.collection.aggregate([{$group:{_id:{customer:"$customer",job:"$job"},chemicals:{$push:"$chemical"},jobTotal:{$sum:"$chemical.quantity"}}},{$group:{_id:"$_id.customer",jobs:{$push:{job:"$_id.job",jobTotal:"$jobTotal",chemicals:"$chemicals"}},customerTotal:{$sum:"$jobTotal"}}},{$project:{_id:0,customer:"$_id.customer",customerTotal:1,jobs:1}}])