After 20+ years of teaching electronics and the advent of inexpensive scientific calculators, I don't much like the idea of folks using truncated approximations for constants. It galls me to watch a student enter 3.14 on a calculator (4 keystrokes) rather than hitting the "pi" key (1 keystroke) for 10 digits of precision; or 1.414 (5 keystrokes) rather than 2 & the sqr-rt key (2 keystrokes) for 10 digits of precision. Granted, you don't need 10 digits of precision for any of these calculations but the time saved alone is worth using the simpler calculator entries.
Besides that, there's less to remember. 3.14159.... is harder to remember than the symbol on the "pi" key; if you need 0.707...., just do [2][sqr rt][1/x] for the full 10 digits of precision -- that's still 2 keystrokes shorter than entering 0.707!
In addition, you'll make fewer errors. I don't know how many times that I've seen a number entered where the decimal point didn't "catch", throwing the calculation off by several decades.
It took me too long to quit making students mule-haul all of their math just for the sake of the math section of the electronic course with the reason that "you'll know more easily if you've made a calculator error". I discovered that I can drive that point home without forcing students to add 1.47 x 10^-6 and 0.00349 x 10^2 by hand.
My time has been better spent teaching the students that dividing 1.81 by 3.0 does not give you an answer with 10 digits of precision even if the calculator does provide 10.
Dean