ITA shows the following +++ for a MIA-YUL-DFW routing on AA (with 36 hours in YUL):US Transportation Tax (US)
$45.75

US September 11th Security Fee (AY)
$5.60

US Passenger Facility Charge (XF)
$4.50

US Flight Segment Tax (ZP)
$8.20

Canadian Air Travelers Security Charge (CA)
$10.00

Quebec Sales Tax (XQ)
$2.00

Canadian Goods and Services Tax (XG)
$1.00

Montreal Trudeau Airport Improvement Fee (SQ)
$19.70

US Customs Fee (YC)
$5.50

US Immigration Fee (XY)
$7.00

USDA APHIS Fee (XA)
$3.96
That's a total of $113.21.