Thanks to Sean Fiene‌ for assistance.

Question: I would like to input a number into a “Single Line Textbox” and have the results show only two decimal places on the View mode of the form.

Step 1:

Create a Nintex Form and add a ‘Single Line Textbox’ configured with a Data type of ‘Decimal’ and name of “RoundNumber”

Step 2:

Add a rule of type “Formatting” with a condition of “Is display Mode” and “Hide”

Formula builder for condition:

Step 3:

Under Nintex Forms Ribbon bar choose “Form Variables”

Click ‘Add’ and create a new variable that includes a formula of ‘Round’ referencing the single line text column of “RoundNumber” and the number of decimal places needed.

Example: Round(roundNumber, 2)

Step 4:

Add a calculated Value control to the form with formula referencing the Forms Variable you created in step 3, in my example it is named “Rounding”.

Step 5:

Create a rule on the Calculated Value Control with formatting condition of “not(Is Display Mode” and choose ‘Hide’

Step 6:

Align the Single Line Textbox and Calculated value controls on top of each other and publish the form.

Results:

Edit Mode:

View Mode: