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 $197.58   5.715%   $208.8717   $208.87   $208.85   $208.90  
  Purchase #2 $212.96   12.382%   $239.3287   $239.33   $239.35   $239.30  
  Purchase #3 $105.55   8.196%   $114.2009   $114.20   $114.20   $114.20  
  Purchase #4 $125.62   6.801%   $134.1634   $134.16   $134.15   $134.20  
  Purchase #5 $38.57   11.605%   $43.046   $43.05   $43.05   $43.00  
  Purchase #6 $151.50   4.717%   $158.6463   $158.65   $158.65   $158.60  
  Purchase #7 $127.97   5.355%   $134.8228   $134.82   $134.80   $134.80  
  7 purchase totals = $959.75       $1,033.0798   $1,033.08   $1,033.05   $1,033.00