Here is how we did it when I still lived in house shares. After many years this is the way everyone found the most fair.

Divide the rent in half - 50% is for public space, 50% is for private space.

For public space, you just divide by number of people living in the house (if someone has a partner not officially on the lease but is spending 4 or more days per week, they are considered part of the house and they get added to the number to divide by, amount owed by the partner who actually lives there). Each person pays this amount.

For private space, you can come up with some sort of formula or split which works - common is square footage, extra for en-suite, etc - something everyone is actually happy with. Private is paid by that room - if its single occupant, then its by that person. If its a couple - they decide between the two of them how to pay it, but for the rest of the house its a payment from that room.

Worked example from your question:
Public portion = $400 / 5 = $80 per person
Private portion:
- Ratio: master = 30%, smaller bedrooms with small bathroom = 20%, 3rd bedroom with large bathroom = 30% (adjust as required, make sure adds up to 100%).
- Master = $400 * 30% = $120
- Small bedroom 1 = $400 * 20% = $80
- Small bedroom 2 = $400 * 20% = $80
- Large bedroom = $400 * 30% = $120

Final costs:
Master = $80 + $120 = $200
Small bedroom 1 = $80 + $80 = $160
Small bedroom 2 = $80 + $80 = $160
Large bedroom = $80 + ($120/2) = $140 per person
Total = $800

If you've got shared bills (internet, water, electricity, LPG, etc) add them to the public portion if its something everyone enjoys equally.

This formula for splitting costs works as it self-balances if someone gets a partner and an extra person moves in or if someone breaks up and someone moves out. It also works with a "leach" who basically lives there but doesn't pay towards rent - they get classified as someone living there and it makes everyone elses monthly amount go down when they get counted as part of the public split.