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 $43.35   8.581%   $47.0699   $47.07   $47.05   $47.10  
  Purchase #2 $240.67   8.796%   $261.8393   $261.84   $261.85   $261.80  
  Purchase #3 $248.25   13.399%   $281.513   $281.51   $281.50   $281.50  
  Purchase #4 $41.83   5.140%   $43.9801   $43.98   $44.00   $44.00  
  Purchase #5 $144.27   9.247%   $157.6106   $157.61   $157.60   $157.60  
  Purchase #6 $206.89   3.774%   $214.698   $214.70   $214.70   $214.70  
  Purchase #7 $185.85   3.351%   $192.0778   $192.08   $192.10   $192.10  
  7 purchase totals = $1,111.11       $1,198.7887   $1,198.79   $1,198.80   $1,198.80