Set the number of displayed decimal places using the DISP key which is [orange-shift] [=].
DISP 2 --> displays 2 decimal places, useful for most financial calculations.
DISP [decimal point] --> same as DISP 11 with trailing zeros automatically suppressed.
DISP [RCL] --> sets DISP 10 mode.
DISP [→M] --> sets DISP 11 mode.
The User's Guide recommends using DISP [decimal point] for displaying results "as accurately as possible".
No matter what your current DISP setting is, you can always view all 12 digits of the result by pressing [orange-shift] [DISP] and then pressing and holding down the [=] key. If you release the [=] key immediately, the 12 digits will be displayed for about 1 second. Otherwise, the 12 digits will continue to be displayed as long as you hold down the [=] key.
Hope that helps! For more details, see your User's Guide.
Disclaimer: I don't work for HP. I'm just another happy HP calculator user.