Yes, the Legislature can override vetoes, including vetoes of line items, provided the legislature has not adjourned, as noted in the Minnesota Constitution Article IV, Section 23. The action must receive a two-thirds majority in both houses (90 in the House and 45 in the Senate) in order to achieve this. There is no limit to this privilege, though successfully overriding a veto has been rare over the course of state history.
Historical data on vetoes and override attempts is available on the Minnesota Legislative Reference Library's Vetoes database.