@Misbah I finally received feedback from Level 3 support. They gave me the following explanation:
Ultimately, as the calculation is 2.2 * 2.2, this will produce 4.840000000000001 as the resulting line item value. The recommendation is to apply the ROUND function with EXACT parameter on the resulting line item value (on the output module and not the system or calculation modules). In the example provided in your screenshots, the ROUND function with EXACT parameter should be applied on the “Use of rounded number” line item as its the resulting line item. The floating decimal precision value is not an Anaplan issue but the way a computer (international IEEE 754 standard) handles calculation. The ROUND function with EXACT parameter was created to address this issue.
This means ROUND can never be used in a central calc model. Instead you will always need to add it to the output module.
I asked them if there is any significant impact on performance doing so. In my case it would be > 200 line items using ROUND instead of 1, but total cell count is similar.