(Adds details on deal) Feb 17 (Reuters) – Takeover target Caltex Australia Ltd said on Monday it would allow Alimentation Couche-Tard Inc to conduct additional due diligence, after the Canadian firm raised its buyout offer to A$8.80 billion ($5.91 billion) last week. Quebec-based Couche-Tard bumped up its cash offer by 2% to A$35.25 a share in a final attempt to sway the oil refiner and convenience store firm after interest from Britain’s EG Group. EG Group has yet to bid, although Caltex said last month the retailer – backed by British private equity firm TDR Capital – had expressed interest in buying some or all of the company. Caltex said the due diligence given to Couche-Tard would be on a non-exclusive basis. Couche-Tard’s revised bid was its third and final offer in the absence of a competing proposal. Caltex turned down two previous offers but provided the firm with non-public information to elicit a better proposal. The Sydney-based firm said in a statement its board believed it was in the interests of shareholders to engage further with Couche-Tard.