Douglas County merchants took in an 11.2 percent increase in taxable sales in September, according to information released by the Nevada Department of Taxation on Thursday.Douglas had $54.5 million in taxable sales during the month, a more than $5 million increase over September 2011.Taxable sales figures are typically released two months after they are collected.This is the second month in a row with double digit increases in sales taxes. In August, taxable sales climbed 10.7 percent to $54.9 million. September was also the first month to see a decrease in sales tax collection since April. September saw taxable sales climb …