The ornamental design for toilet tissue holder, as shown and described.
FIG. 1 is a front perspective view of a toilet tissue holder according to the design;
FIG. 2 is a second front perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a right side view thereof,
FIG. 6 is a left side view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The dotted lines showing of a roll of toilet paper and showing a support holding toilet tissue holder in FIG. 1 are for illustrative purposes only and forms no part of the claimed design.