Rounding strategies are a way to configure Merch Jar to handle sub-cent bid increments. Sub-cent bid increments usually happen when you are doing a small percentage change on a bid that is small. A perfect example of this would be a 5% bid increase on a bid of $0.10. A 5% bid increase would bring your new bid to $0.105, but Amazon doesn't allow sub-cent bids. So, how would you like to handle that? Merch Jar currently has four different rounding strategies.

With this rounding strategy, your sub-cent bids will always be rounding up. So a 5% increase on a bid of $0.10 brings your new bid to $0.105, then the always round up strategy rounds that to $0.11. Similarly, a 1% increase on a bid of $0.10 brings your new bid to $0.101, then gets rounded up to $0.11. This is generally considered an aggressive rounding strategy, as it can increase your bids quickly.

With this rounding strategy, your sub-cent bids will always be rounding down.

- a 5% increase on a bid of $0.10 brings your new bid to $0.105, then the always round down strategy rounds that to $0.10
- a 1% increase on a bid of $0.10 brings your new bid to $0.101, then gets rounded down to $0.10.

This is generally considered a very conservative rounding strategy, as it can keep your bids from increasing. For example, a 5% increase on a bid of $0.10 will never round up to $0.11 with an always round down strategy.

With this rounding strategy, your sub-cent bids will always be rounded "normally". Normal rounding takes any subcent bids greater than or equal to $0.005 and rounds then up to the nearest cent, while rounding subcent bids less than $0.005 down to the nearest cent.

- a 7% increase on a bid of $0.10 brings your new bid to $0.107, then normal rounding rounds that up to $0.11
- a 5% increase on a bid of $0.10 brings your new bid to $0.105, then normal rounding rounds that up to $0.11
- a 4% increase on a bid of $0.10 brings your new bid to $0.104, then normal rounding rounds that down to $0.10.
- a 1% increase on a bid of $0.10 brings your new bid to $0.101, then normal rounding rounds that down to $0.10.

This is generally considered a balanced rounding strategy, although it has the same drawbacks as the always round down strategy in that small bid changes will never be active upon.

Weighted rounding is a bit more complex, but solves the problems associated with the normal rounding and always round down strategies where bids can get "stuck". When you use weighted rounding, your subcent bid is rounded up or down based upon a probability. The easiest way to explain this is to think through a few examples.

If you have a 9% increase on a bid of $0.10, Merch Jar will try to set your new bid to $0.109. The platform will realize this is a subcent bid and it will randomly round that up or down. The chance of a bid rounding up is it's subcent amount, so in this case there is a 90% chance the bid will be rounded up to $0.11 and a 10% chance it will stay at $0.10. A few more examples:

- a 7% increase on a bid of $0.10 brings your new bid to $0.107, giving it a 70% chance of getting rounded up to $0.11 and a 30% chance of staying at $0.10
- a 5% increase on a bid of $0.10 brings your new bid to $0.105, giving it a 50% chance of getting rounded up to $0.11 and a 50% chance of staying at $0.10
- a 4% increase on a bid of $0.10 brings your new bid to $0.104, giving it a 40% chance of getting rounded up to $0.11 and a 60% chance of staying at $0.10
- a 1% increase on a bid of $0.10 brings your new bid to $0.101, giving it a 10% chance of getting rounded up to $0.11 and a 90% chance of staying at $0.10

This is generally our recommended rounding strategy. It is balanced (meaning not too aggressive, nor too conservative) and escapes the caveats that the normal rounding or always round down strategies have.

Tom Myers

Merch Jar Cofounder

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