The Teamsters and United Parcel Service jointly announced a tentative six year agreement today that avoids a threatened strike when the current contract expires at the end of this month (see 'Teamsters Authorize UPS Strike').  The agreement, which must be voted on by the Teamsters membership, provides for an average $5 per hour increase over the six year contract, plus improvements in benefits and 10,000 new union jobs.  The longer term is a plus for retailers that depend on UPS for product deliveries, and was a key negotiating issue for UPS, which wanted to avoid a costly repeat of the 1997 strike; the Teamsters had originally requested a three-year term.   Although the higher wages will probably lead to inevitably higher shipping costs, those marginally increased costs are viewed by most as a small price to pay for reliable deliveries.  Ratification of the contract is almost certain, so smooth deliveries are assured until 2008.