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 $218.92   7.770%   $235.9301   $235.93   $235.95   $235.90  
  Purchase #2 $164.25   11.202%   $182.6493   $182.65   $182.65   $182.60  
  Purchase #3 $222.88   11.595%   $248.7229   $248.72   $248.70   $248.70  
  Purchase #4 $108.61   5.198%   $114.2555   $114.26   $114.25   $114.30  
  Purchase #5 $104.64   10.846%   $115.9893   $115.99   $116.00   $116.00  
  Purchase #6 $112.77   6.757%   $120.3899   $120.39   $120.40   $120.40  
  Purchase #7 $142.81   5.773%   $151.0544   $151.05   $151.05   $151.10  
  7 purchase totals = $1,074.88       $1,168.9914   $1,168.99   $1,169.00   $1,169.00