fix: round exit-prices to proper precision

this avoids odd visualization in freqUI where prices had 16 decimals
out of backtesting

freqtrade/optimize/backtesting.py

@@ -848,9 +848,7 @@ class Backtesting:
                         exit_tag=exit_reason,
                     )
                     if rate is not None and rate != close_rate:
-                        close_rate = price_to_precision(
-                            rate, trade.price_precision, trade.precision_mode_price
-                        )
+                        close_rate = rate
                     # We can't place orders lower than current low.
                     # freqtrade does not support this in live, and the order would fill immediately
                     if trade.is_short:
@@ -892,6 +890,9 @@ class Backtesting:
         self.order_id_counter += 1
         exit_candle_time = sell_row[DATE_IDX].to_pydatetime()
         order_type = self.strategy.order_types["exit"]
+        close_rate = price_to_precision(
+            close_rate, trade.price_precision, trade.precision_mode_price
+        )
         # amount = amount or trade.amount
         amount = amount_to_contract_precision(
             amount or trade.amount, trade.amount_precision, self.precision_mode, trade.contract_size