The pool part
At a pool, the work is the water. Pool Calc's stop screen takes the readings, shows the doses in order for the products on your truck, and logs each one with "Mark as added", including its cost. The client's report shows readings, what was added, the tasks and photos.
Chemical cost per client
Every dose you mark as added stores its cost from the container price on your shelf. Pool Calc's Chemical use & cost screen totals it by client, by pool and by chemical, for this month, last month, the last three months, the year or all time. Export it as CSV and bill chemicals in Jobber or anywhere else.
Using both
Pool Calc and Jobber don't connect. Some techs quote, schedule and bill in Jobber and use Pool Calc at the pool. You'd keep two client lists; Pool Calc imports clients from a CSV file or Contacts to make that quicker.