I live 1.5 hours from the US border in Calais ME. I get all my purchases sent to a parcel depot in Calais. I use the depot address as my mailing address, in connection with their local USPS, Personal mail box (PMB #) for no charge, The depot charges $3 per parcel, and will hold the item(s) there for months without any issues. During Covid, I had some item that were held for over 1 year.
We do trips to Bangor & Portland ME, Haverhill MA, etc every few months, and stay for 1 or 2 nights. Allowed $200 each tax free for 24 hrs, and $800 each tax free for a 48 hr stay in the US.
I have driven over and back, on the same day, and paid the 15% many times if I didn't want to wait for the item. At times, depending on the value bringing back, the Canadian border patrol officers will say, have a nice day and not send you in to pay the tax. I've been doing this since 2010, so the CBP officers are use to seeing me fairly regularly.
Most US border towns have package depots, it's a pretty good gig for receiving and holding parcels. Calais has 3 such package depots.
As long as one has an invoice, receipt for the items, there is no issues at the border coming back to Canada. Often, if I buy poker chips, I ask the seller for a receipt, invoice for that reason, because I have to claim it. One can also make a copy of the private messages if it has the price, or the classified ad. I've never had an issue using a copy of the message or classified ad for a receipt.
Justin always provides an invoice for his group buys.