Most of the exchanges follow a "price-time priority" principle for both orders and quotes. Whenever an order is placed at any exchange, it's given a timestamp which is then used to prioritize the orders. This method of trading is called a Central Limit Order Book or "CLOB" and is used by most of the exchanges globally. We need a system like this to maintain transparency in matching customer orders (bids and offers) on a "price-time priority" basis. The highest bid will be matched against the lowest offer. The global standard also demands that the best 5 bids/offers be seen by all market participants by way of the Snap Quote.
For example, if the price arrived at 27.30 briefly there would've been other market participants who would have placed orders in queue at that price and they would be given priority for execution because they placed their order earlier or had a better price. If you want your order to be executed on priority, it's best to trade at the Market price or you can put a higher/lower Limit price. For example, you can place an order for 27.30 if you would like to be among the first few who get to buy the stock. Conversely, if you would like to sell you can place the order at 27.00 so you get priority over other traders.