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 $114.86   3.819%   $119.2465   $119.25   $119.25   $119.20  
  Purchase #2 $162.80   6.333%   $173.1101   $173.11   $173.10   $173.10  
  Purchase #3 $21.44   5.175%   $22.5495   $22.55   $22.55   $22.50  
  Purchase #4 $117.84   7.295%   $126.4364   $126.44   $126.45   $126.40  
  Purchase #5 $63.39   6.619%   $67.5858   $67.59   $67.60   $67.60  
  Purchase #6 $44.72   10.114%   $49.243   $49.24   $49.25   $49.20  
  Purchase #7 $186.76   4.265%   $194.7253   $194.73   $194.75   $194.70  
  7 purchase totals = $711.81       $752.8966   $752.91   $752.95   $752.70