fix: Update get_amount to return currency precision grand total

In case of multi-currency purchase invoice, we are getting the error "Total Payment Request amount cannot be greater than Purchase Invoice amount" because of rounding difference.

erpnext/accounts/doctype/payment_request/payment_request.py

@@ -15,7 +15,7 @@
 )
 from erpnext.accounts.doctype.subscription_plan.subscription_plan import get_plan_rate
 from erpnext.accounts.party import get_party_account, get_party_bank_account
-from erpnext.accounts.utils import get_account_currency
+from erpnext.accounts.utils import get_account_currency, get_currency_precision
 from erpnext.utilities import payment_app_import_guard
 
 
@@ -540,7 +540,7 @@ def get_amount(ref_doc, payment_account=None):
 		grand_total = ref_doc.outstanding_amount
 
 	if grand_total > 0:
-		return grand_total
+		return flt(grand_total, get_currency_precision())
 	else:
 		frappe.throw(_("Payment Entry is already created"))