Scunthorpe started the better of the two sides with Duane Holmes forcing an early save out of goalkeeper Marek Rodak, but it was Rotherham who opened the scoring in the 17th minute when Taylor latched on to Richie Towell's pass before finding the back of the net.
However, the home side were level within a minute as Ihiekwe diverted the ball into his own net when attempting to clear Holmes's effort which had gone over Rodak.
Chances were few and far between for the remainder of the first half although Scunthorpe did strike the cross bar after the ball was deflected onto the woodwork from a corner.
Rotherham had been second best but Paul Warne introduced Newell just after the hour mark and the change instantly paid off as the midfielder volleyed into the far corner of the net after latching on to an acrobatic flick-on from Towell.
Scunthorpe soon went back onto the offensive and it required a double save from Rodak to keep the Millers ahead with both Holmes and Ivan Toney being denied by the on-loan Fulham stopper.
Ryan Williams drilled a long-range effort marginally wide for Rotherham but Scunthorpe remained in the ascendancy and with a minute of normal time remaining, the hosts found the goal that their play deserved.
A long throw was delivered from the right and after a goalmouth scramble, McGeehan was on hand to force the ball home from close range to leave the second leg at the New York Stadium finely poised.
SCUNTHORPE UNITED (4-4-1-1): Gilks (Watson 62'); Clarke, McArdle, Wallace, Townsend; Adelakun (McGeehan 75'), Yates, Ojo, Morris; Holmes, Toney (Hopper 94')
ROTHERHAM UNITED (4-5-1): Rodak; Emmanuel, Ihiekwe, Wood, Mattock; Vaulks, Taylor (Newell 63'), Towell (Ajayi 72'), Palmer, R.Williams (Forde 96'); Smith