When making small individual tarts it is best to roll your pastry into a log (rather than a disc) before chilling and resting.

When you come to rolling out the pastry, cut the log into slices and then roll out each portion into a round before pressing into the tins. This no-fuss method means there is very little pastry offcuts and no need to re-roll scraps (which often causes the pastry to shrink when baking), ultimately giving you more even tart shell cases.