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 $103.90   10.173%   $114.4697   $114.47   $114.45   $114.50  
  Purchase #2 $169.93   9.768%   $186.5288   $186.53   $186.55   $186.50  
  Purchase #3 $165.62   4.272%   $172.6953   $172.70   $172.70   $172.70  
  Purchase #4 $176.32   6.571%   $187.906   $187.91   $187.90   $187.90  
  Purchase #5 $42.88   8.730%   $46.6234   $46.62   $46.60   $46.60  
  Purchase #6 $228.26   3.232%   $235.6374   $235.64   $235.65   $235.60  
  Purchase #7 $189.74   9.469%   $207.7065   $207.71   $207.70   $207.70  
  7 purchase totals = $1,076.65       $1,151.5671   $1,151.58   $1,151.55   $1,151.50