[Tutor] Some questions about my yen-USD.py

[Dick Moores]

I've just finished a script for converting Yen to USD, and 
vice-versa. A simple, even silly thing to do (a friend asked me to 
write it for him--probably just to humor me), but I have tried to 
build in some bells and whistles. In doing so, some questions arose. 
If some of you Tutors could take look at my script, yen-USD.py, I'd 
greatly appreciate it.   <http://www.rcblue.com/Python/yen-USD.txt>

My questions:

(1) Have I handled possible user-errors OK?

(2) Is my roundingN() function OK? Is there a better way to write it? 
Will the line

        n = round(float(n)*(10**rounding))/(10**rounding)

get me into trouble with the flakiness of float(n)? In testing I 
didn't find any problems, but ..

(3) Is there a better name for roundingN()? I don't like it, but 
can't think of a better one.

(4) I wanted to call closingMessage() in main(), but in some cases, 
if it's in main() it gets 2 successive calls. I can't figure out why. 
Would IDLE's debugger be of use here? (I've never used it before.) I 
haven't been able to find up-to-date IDLE help.

Thanks,

Dick Moores