If you follow the rules that the NFL uses, then both of these teams are technially TIED
with identical .615 winning percentages.
Since 1972, the NFL has counted TIES as 1/2 a WIN and 1/2 a loss, so if you calcuate the winning percentage for an 8-5 team and for a 7-4-2 team, then these teams are considered to have identical
records, just as if both teams were 8-5. The 8-5 record is not
better than than the 7-4-2 record (or vice versa).
If this occurs in the NFL, then the NFL considers the teams tied and proceeds to look at the Division Champion tiebreaker to determine how to break the tie, which is Head to Head record between the tied teams.
So if you follow this process, you should declare the teams tied and use your league's Division Champ tie-breaking procedure, which surely you documented before the season started, right