For multiplying any 2-digit number with another 2-digit number such that the last digit of the multiplier and multiplicand is = 5. The first digits can be different.
For multiplying any 3-digit number with another 3-digit number such that the last digit of the multiplier and multiplicand is = 5. The initial 2 digits can be different.
You can also use this method to multiply numbers with unequal number of digits, i.e. multiplying a 2-digit number with a 3-digit number such that the last digit of the multiplier and multiplicand is = 5.
As long as finding the product of initial digits is easy enough, one can use this method to multiply numbers bigger than 2 or 3-digits.