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Stocks in the US are quoted to 2 decimal places because of reg NMS rule 612 (the subpenny rule). Any displayed quotes above $1.00 are priced in pennies and below $1 you can quote in increments of $0.0001. Trades can however happen in subpenny increments. For example retail internalizers may offer subpenny price improvement (e.g. market is 20.00 x 20.01 - retail market sell order gets filled at 20.0001). Also non-displayed bids and offers may exist at subpenny increments (e.g. market is 20.00 x 20.01 and there is a non-displayed midpoint peg buy at 20.005 at nasdaq - incoming marketable sell will match and print at 20.005).