In E3 there is no simple solution to an optimal buying pattern, if you only achieve discounts if you buy in eaches of for exampel 10.
There is a way solving this problem.
Here is an example:
You can set the quantity discount on the SKU or Item at 10 pieces. When the SOQ is below 10 it will buy 10 SKUs if affordable. When the SOQ is above 10 the problem occurs. The system will not round to the nearest ten pieces.
Normally when buying in large quantites it is almost always affordable to round up to the nearest 10. In that case you could have the described quantity discount and then set the convenience pack to 10. The tricky part is setting the convenience pack break point. You can set this to 99 % and E3 will surely not round SOQ values below ten, but when the SOQ is above ten it will always round to the convenience pack. This means that if in theory SOQ should be 11 it will be rounded to 20 because of the convenience pack setting. Remark, it will never round down.
Settings
Convenience pack = 10
Convenience pack break point = 99 %