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 $104.73   9.185%   $114.3495   $114.35   $114.35   $114.30  
  Purchase #2 $176.53   4.406%   $184.3079   $184.31   $184.30   $184.30  
  Purchase #3 $9.96   8.456%   $10.8022   $10.80   $10.80   $10.80  
  Purchase #4 $169.33   6.234%   $179.886   $179.89   $179.90   $179.90  
  Purchase #5 $154.65   10.109%   $170.2836   $170.28   $170.30   $170.30  
  Purchase #6 $30.85   6.423%   $32.8315   $32.83   $32.85   $32.80  
  Purchase #7 $11.48   3.265%   $11.8548   $11.85   $11.85   $11.90  
  7 purchase totals = $657.53       $704.3155   $704.31   $704.35   $704.30