In Ibsen's A Doll's House, Nora continuously tells lies, with their seriousness varying from that of petty "white lies" to far more serious deceptions.
In the beginning of the play, Nora lies about relatively silly things, telling Torvald that she hadn't consumed any sweets when he asks her, "Hasn't Miss Sweet Tooth been breaking rules in town today... taken a bite at a macaroon or two?" This is a harmless lie... the kind of mistruth that an audience understands could be easily forgiven. It's a habit that seems to play an important role in the dynamic of Nora and Torvald's relationship; she bends the truth in order to avoid his gentle scolding, and the entire thing plays off as an inside joke, with Nora continuing to act as his "little featherhead," "little skylark," or "little squirrel." It's easy to write these lies off as facets of Nora's childishness or her ineptitude in understanding the big, complicated work of her husband.
In reality, however, Nora is not inept; while she may pretend to not understand their financial situation, she knows that they are in trouble. Still, Nora believes that her large lies are an act of love and necessity; she wants to protect her husband from the truth, claiming:
It was necessary he should have no idea what a dangerous condition he was in. It was to me that the doctors came and said that his life was in danger.
This hidden knowledge of the gravity of her husband's illness is what drives Nora to commit her next act of fraudulence: forging her dead father's signature in order to take out a loan to finance a trip to Italy where Torvald may properly recuperate... and lying to Torvald that she received the money directly from her father.
Torvald later chalks up this lie to a woman's child-like dependence on her husband, but it is here that Nora's true personality comes out: she is not a child and does not wish to rely on Torvald. She longs to develop her own identity, a sense of her "self," and a purpose for her life beyond marriage and motherhood. Although her larger lies were truly acts of sacrifice on her husband's behalf, she can now see that this is not the type of thing he values or appreciates, and that their marriage itself has been an act of mutual deception.