A method is provided for personalizing security conditions for each customer using a self-service checkout terminal to conduct a transaction on the terminal. A trust level is assigned to each customer based on a selection of factors, which may include personal information provided by the customer, factors independent of the customer, such as information specific to the particular merchant, and the customer's history in using the checkout terminal or other facilities of the merchant. The manner in which the transaction progresses for the customer is determined as a function of the customer's trust level. In one example, the weight tolerance applied to products weighed by the customer may be widened or narrowed in relation to the customer's trust level.