Your issue seems to be related to Price and linked to GL Currency conversion and rounding. Basically you are creating a requisition with foreign currency and don't want to restrict the rounding to 2 decimal places.
You can address this issue by setting up the precision under Currencies setup of GL for SGD (GL --> Setup --> Currencies --> Define --> Change Precision as per your requirement) . But the risk is, this change in precision will affect across all modules. It is widely accepted to use rounding to 2 decimal places.