One of the best and most trusted ways of increasing the average transaction total is by implementing many special offers across the store. These can be as straightforward as mix and match, to two or more products that complement each other.
Offers can be limited by certain restrictions e.g. dates or time of day, loyalty customers only, certain stores etc. Offers can also be set to only work a limited number of times, great for buying a pallet of a product cheap and ensuring only those items are sold at a reduced rate.