Looking at DFW-SLC nonstops on AA at matrix.itasoftware.com, the cheapest roundtrip fare (three weeks from now) appears to be $368.40, including $5 security, $9 PFC, $6.40 segment tax and $24.28 excise tax. Assuming the first three of these don't change, you're left with $16.01 excise tax, so your base fare was $213.46. Actually, I suspect it was $213.49 because most airlines try to make the amount including excise tax a round number, and that still incurs $16.01.

So your figure for accounting is $229.50 plus $20.40 in taxes, i.e. $249.90.

Be aware that the Pricelines of this world have been known to manipulate the tax amounts to conceal what they really paid for the seat -- no idea if Expedia did that this time, but '$124.95 each way' sounds pretty much like marketing-speak to me, so it's probably accurate