Many users who use Gixen for the first time are under the false impression that it's Gixen that does incrementally and raises your bid as needed. This is incorrect - this is eBay's own feature and it's called eBay Automatic bidding (or ebay proxy bidding). Sniping services place your bid at a predetermined time, and have some additional features and benefits, which I will describe below, however incremental bidding is not one of them. You will still benefit from it, however, only it's eBay that provides this for you, not Gixen, and this takes place on eBay's servers after Gixen places a bid for you. As a result, you will never pay more than you have to in order to win an item.
Once your bid is placed on eBay, Ebay will look at the current high bid and compare it to your maximum bid. If your maximum bid is equal or higher to the current high bid + bid increment, eBay will accept your bid. After your bid is accepted, one of two things can happen - if your maximum bid is higher than the current high bidder's maximum bid, you will become the new current high bidder. Otherwise you will be outbid and the current high bid will move up to your maximum high bid + bid increment. A caveat here is - if the current high bidder's maximum bid is less than an increment higher than your maximum bid, the winning bid will be less than an increment higher, and possibly identical to your maximum bid. Your maximum bid always remains a secret, until you are outbid. If you win the auction, no one except you, eBay (and Gixen if you use it) will ever know what that maximum bid was. The opposite is also true - if you lose an auction, you will not know what the winning bidder's maximum bid was.
It's a common misconception that the closer to the auction end your bid is placed, the better. This is true only up to a point. Sniping is great, and it saves you money, however it helps you only against manual bidders by not leaving them enough time to react to your bid, think it over and submit another, higher bid. However it does nothing against other pre-scheduled bids. For these, bidders have already determined their maximum, they are also submitting their bid automatically, and they don't plan (or have time) to change their mind anyway. Against other snipers you want your bid to come before their bid, so that eBay's bid increments work in your favour. Most snipers submit their bids 6 seconds before the auction ends or less. My own personal favourite offset is 8 seconds. This ensures that my bid is at eBay before other snipers, yet it's short enough that manual bidders don't have time to detect my bid, change their mind and re-submit their own, higher bid.
Opinions on this differ, and it's a never-ending discussion that you can often find on the Gixen's community forum.
For a more detailed explanation on how eBay's bid increments work, see this blog post: https://www.gixen.com/blog/ebay-bid-increments/
Auctions can sometimes have a Buy-it-now or "Best Offer" option. These options typically disappear after the first bid is placed. In case of Buy-It-Now price, eBay will not allow bids higher than buy-it-now price until the option disappears. When users bid higher than buy-it-now through Gixen, Gixen will try to submit the original maximum bid. If this fails, it will immediately re-submit Buy-It-Now price - 0.01.
For related articles, please see:
eBay proxy bidding and bid increments: https://www.gixen.com/blog/ebay-bid-increments/ Bid shielding: https://www.gixen.com/blog/bid-shielding-ebay/