英语 翻译 表示上下浮动on a recdent trip, cindy drove her car 290 miles

英语 翻译 表示上下浮动
on a recdent trip, cindy drove her car 290 miles, rounded to the nearest 10miles,and used 12 gallons of gasoline, rounded to the nearest gallon.the actual number of miles per gallon that cindy's car got on this trip must have been between~
这段话的精确翻译
重点是rounded to the nearest 10miles 这句是上下浮动10miles的意思吗?

rounded to the nearest gallon 这句又怎么讲