Deuteronomy 25:16: For all who do such things, all who act dishonestly, are an abomination to the LORD your God.
God detests dishonesty and Moses in the focus verse was laying down the ground rule for the nation of Israel concerning relationship with one another especially as regards honesty in trading.
Using just/consistent/appropriate/accepted weights and measurement is honesty, not twisting or manipulating the measurement system for the undue gain. That is taking undue advantage of the people. It is dishonest; it is deceptive and unacceptable to God.
Having a business setup where there is fair gain derived from your customers is a recipe for success. You don’t want to overcharge in the name of making profit, make all manner of false claims just to hoodwink the buyer into parting with his hard-earned money. For you it should not just be about the bottom-line, as important as that is, but your customers should not just leave with service rendered or goods purchased, but with a good feeling that you have obviously expressed your concern for his/her best interest from heart.
Acting dishonestly is abominable to the Lord said the focus verse. You are not permitted in the kingdom of God to act anyhow; we are not permitted to conform to this world with their dishonest standards and pursuit of dishonest gains, through taking undue advantage of people’s vulnerability. You are not to mislead others. You can’t do it because that is what others do (Exodus 23:2). You are different.
You are called to be transformed by the renewing of your mind (Romans 12:2). We should be transformed by realising that in the kingdom of God in which we are as Christians, there is a king who should be obeyed, whose name is Truth (John 14:6), and He wants us to act true to who he is. But the devil, we are told is liar and the father of lies (John 8:44).
One of the Ten Commandments is: you shall not bear false witness (Exodus 20:16). You should exhibit openness, purity and evenhandedness in your dealings, not showing favouritsm. The judges were not supposed to receive bribes, with which to blind their own eyes in the course of justice (Exodus 23:8, Deuteronomy 16:19, Proverbs 17:23). The bible says: woe is he who calls good evil and evil good, which is a call for purity in our dealings. The right thing is the right thing, which is what we should do all the time.
Can you be described as honest? If not, then you have some adjustments to make and quickly too. There is an example of a dishonest man in the bible who paid dearly for it.