Denver voters will be asked in November to consider increasing the city’s sales tax to raise $70 million a year to help stabilize Denver Health, the region’s financially ailing safety-net hospital. The Denver City Council voted 12-1 without discussion Monday to send the .34% sales-tax increase — which would add 34 cents to a $100 purchase — to the ballot. The city’s current sales tax is 8.81% and, if this measure is approved by voters, it will increase to 9.15%. Councilman Kevin Flynn, who represents District 2, cast the only dissenting vote.