Looks correct.

Another idea would be simply to round the point to the grid and compare:

bool CheckPointInTile (vec2 point, int tileX, int tileY)
{
	return ( 	(int)floor(point.x) == tileX) &&
				(int)floor(point.y) == tileY) );
}

Requires grid and points share the same coordinate system ofc.