TOKYO, June 30 (Reuters) - The yields on 10-year Japanese government bonds gave up early gains to end unchanged on Wednesday, after the Bank of Japan trimmed the amount of bonds it will purchase in the coming quarter. The 10-year JGB yield closed at 0.055% after rising to 0.060%, while the 10-year JGB futures fell 0.01 points to 151.68, with a trading volume of 15,824 lots. The 20-year JGB yield rose 0.5 basis points to 0.440%. The 30-year JGB yield was unchanged at 0.685%. The 40-year JGB yield rose one basis point to 0.765%. The two-year JGB yield was also flat at minus 0.115%, and the five-year yield was unchanged at minus 0.100%. (Reporting by Tokyo markets team; Editing by Kenneth Maxwell) Our Standards: The Thomson Reuters Trust Principles.