  The 'minimal' payment - a payment method which minimizes the number of coins
in a purse - is presented. We focus on a time series of change given back to a
shopper repeating the minimal payment. The delay plot shows visually that the
set of successive change possesses a fine structure similar to the Sierpinski
gasket. We also estimate effectivity of the minimal-payment method by means of
the average number of coins in a purse, and conclude that the minimal-payment
strategy is the best to reduce the number of coins in a purse. Moreover, we
compare our results to the rule-60 cellular automaton and the Pascal-Sierpinski
gaskets, which are known as generators of the discrete Sierpinski gasket.
