Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $176.88   13.603%   $200.941   $200.94   $200.95   $200.90  
  Purchase #2 $167.41   9.121%   $182.6795   $182.68   $182.70   $182.70  
  Purchase #3 $146.97   11.294%   $163.5688   $163.57   $163.55   $163.60  
  Purchase #4 $233.92   3.634%   $242.4207   $242.42   $242.40   $242.40  
  Purchase #5 $101.61   12.444%   $114.2543   $114.25   $114.25   $114.30  
  Purchase #6 $167.47   5.333%   $176.4012   $176.40   $176.40   $176.40  
  Purchase #7 $117.38   8.533%   $127.396   $127.40   $127.40   $127.40  
  7 purchase totals = $1,111.64       $1,207.6615   $1,207.66   $1,207.65   $1,207.70