The Ten of Pentacles (Ten of Rocks in the Penguin tarot deck) is the card that represents true wealth, as well as being financially secure, and having a secure and stable family. It also represents being a contributing member of society as well as success being in the long-term. The Tens are the completion number of any of the suits. The Pentacles is the material suit, and this card is the one that shows that the success and financial stability and wealth you have is in the long term.
the Nine of Pentacles indicates that you have earned your wealth, and this card shows that the wealth you have earned is here to stay. An example is you had started a furniture company from scratch. And you built your business up so well that you have built wealth through it for years, and the company is there to stay. You can provide for your family, and this wealth has given you the stability you need.
The Ten of Pentacles can also represent an inheritance. If you gain a large inheritance, you will be comfortable financially for a long time.
The Ten of Pentacles reversed can show the dark side of being wealthy, where only money is valued and nothing else. It can also represent a company that was one successful failing and declaring bankruptcy. It can mean financial loss.
Astrologically, this card is tied to Mercury in Virgo.