All orders have to be a round number of satoshis (.00000001 BTC). The minimum quantity is .00001 BTC, or 1000 satoshis. All prices need to be a round number of cents, that is, the tick size is $.01 or one penny.
The minimum quantity is .001 ETH. The smallest allowable quantity increment is 0.000001 ETH. For example, you can place an order for 0.001001 ETH, but not 0.000999 ETH.