Since you are using a SWG, your TA level is just perfect where it is.
Your PH might actually be lower than 6.8, since the common PH test will read lower PH as if it was 6.8. I would add one box of borax, give it an hour to mix in, test your PH to see where it is, and keep doing that until your PH is above 6.8. Hopefully that will only be one box. Once your PH is above 6.8, adjust it from there to 7.2.
Your PH might actually be lower than 6.8, since the common PH test will read lower PH as if it was 6.8. I would add one box of borax, give it an hour to mix in, test your PH to see where it is, and keep doing that until your PH is above 6.8. Hopefully that will only be one box. Once your PH is above 6.8, adjust it from there to 7.2.