The Four of Pentacles (Four of Rocks in the Penguin tarot deck) represents the frugal living, saving money, being conservative with your spending, as well as keeping control of money. It can have two meanings. If you are appreciating the wealth you have accumulated, you are purposely living a frugal lifestyle so you can save money for what you really want. However, it can also mean living in a mindset of lack and being cheap.
The way the Four of Pentacles plays out depends on the other cards that surround it. If the cards that surround this card represent abundance, then you would simply live a frugal lifestyle to save up for the beautiful things you want. Frugality is not the same as being cheap, as everyone should live a frugal lifestyle. It means you are careful with what you spend but you will not hesitate to buy items that are of good quality that you will need.
However, the other side of Four of Pentacles shows that you are believing that you are poor and you have to hang onto every penny. You are not living frugally. You are cheap by buying the lowest quality products in small quantity which means you are barely living. Again that depends on the surrounding cards whether you are living a frugal lifestyle or hanging on to every penny you have.
If you have the Four of Pentacles in reverse, then it can either mean you are overspending and not watching your dollars. Or, it can also represent living in a lack-mindset where you are hanging onto every penny, as it can in the upright position.
Astrologically, this card is tied to the Sun in Capricorn.