I have a share of Audi, and have been puzzled by the fact that beginning with January 2018 until now, it has always had whole even Euro values – currently 804.00 €. How is this possible? What keeps traders from selling at different prices?
I wrote to Audi Investor Relations and they provided a quite detailed answer. It turns out that there are "tick sizes" for shares as per European Union regulation 2017/588, which came into effect from 2018 on and has larger tick sizes for for expensive shares and shares with lower trade volumes; hence it is especially noticable for an expensive share with very limited free floating shares (0.36 %) like Audi's.
The table of tick sizes for various price ranges is found in the annex.
Some exchanges have quotation rules that could force that to happen. Audi is listed on several exchanges, some European, some US. On the US exchange there are plenty of quotes that are not even numbers.
There could also be liquidity issues on some exchanges.
There could also be the fact people just don't want to trade at non-even prices, which could be related to liquidity issues.
I'm puzzled by your question. The link that you provided opens up a chart which defaults to one day (no chart). If you click on any number of days other than one day. it displays a graph of different prices on different days.
On the days when there were no trades, the close remains the same and the graph is horizontal.
You can see the historical prices and daily volume at Yahoo Finance.