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 $148.84   5.660%   $157.2643   $157.26   $157.25   $157.30  
  Purchase #2 $163.98   7.840%   $176.836   $176.84   $176.85   $176.80  
  Purchase #3 $76.93   3.339%   $79.4987   $79.50   $79.50   $79.50  
  Purchase #4 $241.90   3.292%   $249.8633   $249.86   $249.85   $249.90  
  Purchase #5 $228.49   5.853%   $241.8635   $241.86   $241.85   $241.90  
  Purchase #6 $43.41   10.158%   $47.8196   $47.82   $47.80   $47.80  
  Purchase #7 $144.82   5.575%   $152.8937   $152.89   $152.90   $152.90  
  7 purchase totals = $1,048.37       $1,106.0391   $1,106.03   $1,106.00   $1,106.10