2017 infiniti QX60 How to calculate taxes into monthly

I have been working with different dealers in the area and this is the best offer I have received by far. I was planning to head over there tomorrow although I have heard I should hold out until after Christmas since it is Triple Quota Saturday Dec 31. Advice? It is the car my wife wants and they are trading with another dealer to get it. (Same dealer, different city)

MSRP $46610
Sale Price $38610
39/12k

I was quoted $392/month with $4k upfront ($2,700 taxes 7%, $830 reg and doc fee, 1st month $392)

Here is the question. I want to roll this 4k or at least just the taxes(2700) into the monthly payment and instead use 9 MSD’s ($3150) to lower the MF.

How do I calculate if I want to roll these fees into the monthly? I only have about $4k to pay upfront is why. Can I simply add it into the sales price on the lease calculator? If I take 2703/39= $69.31 but I know this isnt accurate.

GA requires us to pay taxes on the sale price of vehicle.