Why can't I see an exact zero reading?

When I send the command to zero or tare the scale the weight reading is not exactly zero. The weight reading goes to a value between +0.05 and -0.01 lbs, and the 3 load cells are 2000 lbs each. Why can't I see an exact zero reading?

What you are seeing after sending the command is the fluctuation in the weight reading.  The unit will go to zero, but then fluctuate around the zero point.

When you TARE or ZERO the Net or Gross weight, the reading will go to ZERO. The load cells will fluctuate or settle within its resolution tolerance and displays that weight. For your scale the resolution is set to two decimal places, you will not see 0.00 lbs due to your low resolution and high tolerance. If you remove the decimal points the zero net weight readings will not be a problem. Let me explain below.

With two decimal points the scale is reading beyond it's design limits in trying to reflect the requested weight resolution. In your case the total of the three load cell's capacity (3 x 2000) is 6000 lbs. If you divide that by the expected stable and repeatable weight reading of a load cell (1 in 10,000) it will give you the expected weight repeatability (or maximum fluctuation). So, maximum capacity divided by resolution = fluctuation. (6000/10000=0.6) Your repeatability is 0.6lbs and that is what is the specified stable weight reading.  This means you may see fluctuations up to 0.6 lbs.  If you zero or tare the scale, you may see the weight reading anywhere within this 0.6 lbs range of the zero point.

Your scale should set for one decimal point and a graduation size of 5.  This will give readings in 0.5lb increments.

Adding decimal point beyond the design limits will not provide additional resolution.   You can add many averages and large WaverSaver settings, but that adjustment will delay your weight readings and could over fill your vessel.