Nieminen took a stronghold in the opening set by snatching a crucial break point to elevate his confidence on the court to put Raonic on the back foot.
He continued to display swift forehands and damaging returns to maintain his lead and snatch the opening set, leaving his Canadian opponent with it all to do in the second set.
Despite an early blow, the 22-year-old responded by holding his serve well and breaking his opponent in the second game to swerve the match in his favour.
Nieminen could only put one game on the board and succumbed to a damaging defeat, leaving it all square, with one final set left to decide the winner.
Both competitors held their serves and committed powerful returns to keep the set going by the way of serve, until a tie-break was needed to decide the winner.
Despite positive play from both competitors throughout the clash, it was Nieminen who came out on top in the tie-break to book a place in the next round.