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 $208.76   7.513%   $224.4441   $224.44   $224.45   $224.40  
  Purchase #2 $44.57   3.756%   $46.244   $46.24   $46.25   $46.20  
  Purchase #3 $205.65   3.455%   $212.7552   $212.76   $212.75   $212.80  
  Purchase #4 $178.38   7.108%   $191.0593   $191.06   $191.05   $191.10  
  Purchase #5 $194.98   6.461%   $207.5777   $207.58   $207.60   $207.60  
  Purchase #6 $233.63   3.243%   $241.2066   $241.21   $241.20   $241.20  
  Purchase #7 $114.37   10.836%   $126.7631   $126.76   $126.75   $126.80  
  7 purchase totals = $1,180.34       $1,250.0500   $1,250.05   $1,250.05   $1,250.10