There is only One Priest who can forgive sins against God, and that is Jesus Christ.
We are all called to repent of our sins to Christ as He is the One who paid for our sins, and God is the Only One who can forgive sins. This includes confessing that we are guilty, that what we did was wrong and that we are sincerely sorry, and it means that we turn away from it, praying for God's help to do so. This is what we are to do when we sin.
Confessing to "each other" is for our benefit...it is a blessing to us...so that we can support our brothers and sisters in their struggles with this world, and the sins we all have problems with. It provides opportunity for accountability and prayer. We can all relate to each other's confessions because we all have something to confess at all times as no one is perfect while we live in these fleshly bodies.
James 5:12-20
12 Above all, my brothers, do not swear--not by heaven or by earth or by anything else. Let your "Yes" be yes, and your "No," no, or you will be condemned. 13 Is any one of you in trouble? He should pray. Is anyone happy? Let him sing songs of praise. 14 Is any one of you sick? He should call the elders of the church to pray over him and anoint him with oil in the name of the Lord. 15 And the prayer offered in faith will make the sick person well; the Lord will raise him up. If he has sinned, he will be forgiven. 16 Therefore confess your sins to each other and pray for each other so that you may be healed. The prayer of a righteous man is powerful and effective. 17 Elijah was a man just like us. He prayed earnestly that it would not rain, and it did not rain on the land for three and a half years. 18 Again he prayed, and the heavens gave rain, and the earth produced its crops. 19 My brothers, if one of you should wander from the truth and someone should bring him back, 20 remember this: Whoever turns a sinner from the error of his way will save him from death and cover over a multitude of sins.
Take Care and God Bless!
Addition, there is "NO" amount of penance that a person can do to be forgiven their sins. No one deserves salvation and no one earns it by doing penance. If penance were a way to be forgiven for our sins, then we could all simply pay the fee on our own and Christ would never have had to die on the cross to pay the penalty for us.
Ephesians 2:4-10
4 But because of his great love for us, God, who is rich in mercy, 5 made us alive with Christ even when we were dead in transgressions--it is by grace you have been saved. 6 And God raised us up with Christ and seated us with him in the heavenly realms in Christ Jesus, 7 in order that in the coming ages he might show the incomparable riches of his grace, expressed in his kindness to us in Christ Jesus. 8 For it is by grace you have been saved, through faith--and this not from yourselves, it is the gift of God-- 9 not by works, so that no one can boast.
Also the Holy Spirit was given to us to "help" us in our struggles with sin, and to sanctify us. Human beings cannot forgive one another's sins against God. If we break God's law, there is only "One" sacrifice for our sins. One for all. Jesus Christ.
Also: When the Apostles were given the ability to forgive men their sins, the context was that they had the ability to give the offer of salvation to the Jews "and" the Gentiles which according to the Jewish understanding, were not allowed to be offered salvation because they were not Jews.
The apostles were also given the ability to cure disease, heal the blind, the lame, the deaf, cast out demons, and even resurrect the dead.
All of these gifts are of course possible with God, but they are not commonplace in this age because we are to have "faith" in Christ according to His word.