I've used tarps to cover our tractors for years. They aren't perfect, but a couple of tricks do help.
One is that tarps have changed from the old wax impregnated cotton fabric to a newer and better polyester/cotton blend that is lighter, silicon coated, doesn't smell or rot and is breathable. Being breathable is very important.
All the tarp companies carry this new poly/cotton tarp in about 15oz weight. It's the only way to go. ChicagoCanvas.com calls it their "iron horse" cover.
Polyester Tarp - Iron Horse - Waterproof Tarp. Other suppliers have their own trade name.
I buy from TarpSupply.com
They call their polyester-canvas.
Whatever you call it, this new materials costs as much as double what a traditional smelly heavy waxed cotton tarp costs, but definitely worth it. Long lasting and breathes.
Second, tarps are described by the size that they are cut from the roll. They lose about 6 to 9 inches in width and length when seamed for grommets. You want brass grommets. Industry std. is every 18 inches.
These new polyester/cotton blend tarps are lighter and more flexible, but still bulky to put on and take off. A 7x9 foot (actual) is about all I want to handle on an every evening basis. Over 10x10 would be a hassle. Do the minimum. Measure using an old sheet. Keep it way up off the ground. If it only covers to half way down the sides of the tractor that is about perfect because then it breathes and critters stay away.
Finally, if you tarp every evening put some thought into the fastening. Tarps take a set, so you want it to go on the same way each time.
Adjustable clips should that stay on the tractor instead of being on the tarp so aren't in the way and catching on everything when you put the tarp on and take it off.
I use Nite Ize CamJam R3 size. Handy, adjustable, and they are big enough to grab the grommets. Their cord is fastened to the tractor and when not in use just clip them out of the way,
Bottom line is any kind of shelter is better, but a tarp can work OK if you set it up right to just cover the top and half way down the sides.
rScotty