Hmmm... If it's the MS-DOS version of TurboTax, you'd probably be better to use either DosEMU or DOSBOX.
PC-0-10 and PC-0-11 were deprecated with the release of QEMU 3.0 - and PC-0-12, PC-0-13, PC-0-14 and PC-0-15 are deprecated by QEMU 4.0.
Also, looking through the change for that *addition* of PC-0-10 reveals this was added to:
Add a pc-0-10 machine type to allow a pc machine to be created with virtio block and console devices compatibilty with qemu-0.10.x.
So it's more of a driver compatibility issue than anything else.
Looking at the downloads on the QEMU source downloads website, 0.11.1 was released in December 2009 - or there abouts. (0.11.0 was released in March) 0.15 takes us up to about August or October 2011. (0.15.0 and 0.15.1, respectively)