How can I pan a texture to specific location on a sheet?

Unfortunately I haven't used Shader Graph yet but in HLSL and CG there are many ways to do that and I would guess that at least one of them is also possible in Shader Graph. All of them are based on the same idea: have a float value that increases over time but then make it 'jump' through integers instead of increasing it gradually. That value can then be used in some formula to determine the texture offset.

trunc, ceil, floor, round: Functions that find a integer for a float according to different rules.

float f1 = trunc(_Time.y);   // cut off the decimals
float f2 = ceil(_Time.y);   // next integer above
float f3 = floor(_Time.y);   // next integer below
float f4 = round(_Time.y);   // closest integer

int cast: Converts a float to an int, following the same rules as trunc except that the data type changes here, while trunc still returns a float.

int i = (int)_Time.y;

remainder: Gives the remainder of integer division, use it with 1 as second operand and subtract it from the original value to get an integer

float f = _Time.y - _Time.y % 1;