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 $32.46   13.119%   $36.7184   $36.72   $36.70   $36.70  
  Purchase #2 $214.86   12.369%   $241.436   $241.44   $241.45   $241.40  
  Purchase #3 $103.81   10.527%   $114.7381   $114.74   $114.75   $114.70  
  Purchase #4 $58.68   10.103%   $64.6084   $64.61   $64.60   $64.60  
  Purchase #5 $183.33   5.468%   $193.3545   $193.35   $193.35   $193.40  
  Purchase #6 $43.31   5.539%   $45.7089   $45.71   $45.70   $45.70  
  Purchase #7 $58.53   12.175%   $65.656   $65.66   $65.65   $65.70  
  7 purchase totals = $694.98       $762.2203   $762.23   $762.20   $762.20