Running Mac OS Tiger on Yosemite
You will not be able to install OS X Tiger on a modern Mac due to lack of hardware driver support.

Apple's license agreement for OS X did not allow virtualization at all until Snow Leopard Server and Lion, so virtualization software such as VirtualBox, VMWare Fusion, and Parallels Desktop do not support running Tiger in a Virtual Machine.

If you need to run Tiger, your best bet is purchasing an older Intel Mac that shipped with Tiger or a PowerPC Mac that supports Tiger.