If you have been going with your town for a while and start to creep up on the town inventory limit, you might be inclined to sell of some of your stuff. But that doesn’t help very much, scince you’ll get baskets of gold coins in return for any trade you make, you’ll still have to store those as items.
So my suggestion is two more types of currencies; basket of platinum coins and basket of diamonds (respectivly worth 10 and 100 times as much as a basket of gold coins) to condense the same monetary value into less items.
To convert the gold to platinum or diamonds, you need to buy it from an currency merchant. If you need to pay another merchant gold, but all you have is platinum, you can trade 10 gold from the merchant for ten gold, and pay with that gold for what you want to buy.