I have this pump, which is very well-reviewed albeit a bit cheap:
Amazon.com: Schwinn 5-in-1 Floor Pump

When I pump up my tires I will get it to about 85 PSI and then I will release the lever to remove the pump from the valve. When I do that I hear air hiss out and so I quickly try to take it off, but it always takes a second because it kind of sticks. Then I am thinking I deflated the tires too much so I put the pump back on, hear some air hiss while I lock down the adapter, and it reads about 65-70 PSI. So my stupid noob question is this: when I disengage the pump each time am I releasing some air from the tires? If so, should I pump up the tires to a higher PSI than I actually want?

Any other tips on something so incredibly basic that I am kind of embarrassed to ask it on a public forum?