文章出处：
http://evaevazhuxun.blog.sohu.com/154543859.html
http://blog.sina.com.cn/s/blog_a4034b2801012o1n.html
1.roundn
a=123.4567890;
a=roundn(a,-4)
% 返回 123.4568
Round numbers to specified power of 10
2.round
函数简介
调用格式：Y = round(X)
在matlab中round也是一个四舍五入函数。在matlab的命令窗口中输入doc round或者help round即可获得该函数的相关帮助信息。
相关函数：ceil、floor、fix
程序示例
>>a = [-1.9, -0.2, 3.4, 5.6, 7.0, 2.4+3.6i]
a =
Columns 1 through 4
-1.9000 -0.2000 3.4000 5.6000
Columns 5 through 6
7.0000 2.4000 + 3.6000i
>>round(a)
ans =
Columns 1 through 4
-2.0000 0 3.0000 6.0000
Columns 5 through 6
7.0000 2.0000 + 4.0000i
a =
Columns 1 through 4
-1.9000 -0.2000 3.4000 5.6000
Columns 5 through 6
7.0000 2.4000 + 3.6000i