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 $114.44   10.867%   $126.8762   $126.88   $126.90   $126.90  
  Purchase #2 $151.49   10.189%   $166.9253   $166.93   $166.95   $166.90  
  Purchase #3 $69.38   8.788%   $75.4771   $75.48   $75.50   $75.50  
  Purchase #4 $215.99   11.692%   $241.2436   $241.24   $241.25   $241.20  
  Purchase #5 $215.61   8.385%   $233.6889   $233.69   $233.70   $233.70  
  Purchase #6 $170.94   8.735%   $185.8716   $185.87   $185.85   $185.90  
  Purchase #7 $68.96   5.147%   $72.5094   $72.51   $72.50   $72.50  
  7 purchase totals = $1,006.81       $1,102.5921   $1,102.60   $1,102.65   $1,102.60