What the OP is talking about is called Parallax.
The most important thing you need to know is that Tasco is owned by Bushnell, which is owned by Bausch and Lomb..
There is only a couple of machines that makes the optics for all of the rifle scopes made in the world.
The difference today between a relatively inexpensive scope and a professional quality scope is the quality of the optics, the quality of the adjustment and the coatings applied to the lens.
The Tasco has a reputation of being a very inexpensive rifle scope that has poor quality and shoddy workmanship.
In fact, most of the Tasco Rifle Scopes I have used, failed to pass a simple warm water immersion test.
Basically if you wanted a new scope, all you had to do was remove the turret covers, immerse the scope in warm water for 5 minutes, watch the air bubbles in the tub of water. The warm water would be drawn into the workings of the scope, Destroying the scope. Usually the lens would fog and the manufacturer would replace the scope, as per their warranty.
What happened was that Tasco went out of business and Bushnell had no competition, no competition equaled a loss of sales. So they bought the company, design, name, and started producing a better quality scope with the Tasco brand.
The Leupold Rifle scope, not pronounced LeoPold, but LOO Pold, is of a high quality then the cheaper brands.
Although the Rifleman - $200 scope that Pa Waterfowler mentioned does not fit into this category. As a matter of fact, Leupold doesn't even make that rifle scope, and over the years, counterfeit Leupold rifle scopes has been sold, which the manufacturer will not honor it's warranty.
Leupold entered the Rifle Scope market in 1907 at Leupold, Volelpel, adding Stevens in 1914 in Portland, Oregon.
After World War II - Leupold began to produce commercial rifle scopes. Most of their target rifle scopes were produced with a fixed power. The less moving parts, the less there was to go wrong with the scope, and it eliminated Parallax.
Another company called Redfield, was also in the rifle scope manufacturing business, based in Beaverton Oregon..
Their claim to fame was in producing a high quality rifle scope with a T.V. - Wide Field View.
These scopes were used in early production sniper rifles used in the Vietnam War. When the soldiers came home, they demanded this very same rifle scope for their hunting rifles. Sometimes doubling the cost of the hunting rifle!
Note - I said HUNTING.
Deer Hunters doesn't really need a scope that can shoot 1000 yards, or kill paper targets. The Redfield Widefield allowed the average hunter the ability to shoot in difficult situations, which the cheaper Weaver fixed power rifle scopes were not suitable for, such as low light conditions, rain, fog, etc..
Same story as Tasco, when Redfield went out of business in 2008, Leupold bought the name and the company.
Basically you get what you paid for, if you buy a cheap scope - you can't expect durability or accuracy.
Today there is only a hand full of company's in The USA that still makes their own rifle scopes.