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 $93.64   4.698%   $98.0392   $98.04   $98.05   $98.00  
  Purchase #2 $104.76   8.798%   $113.9768   $113.98   $114.00   $114.00  
  Purchase #3 $67.77   6.507%   $72.1798   $72.18   $72.20   $72.20  
  Purchase #4 $32.75   5.560%   $34.5709   $34.57   $34.55   $34.60  
  Purchase #5 $114.40   6.564%   $121.9092   $121.91   $121.90   $121.90  
  Purchase #6 $216.38   4.296%   $225.6757   $225.68   $225.70   $225.70  
  Purchase #7 $94.93   5.563%   $100.211   $100.21   $100.20   $100.20  
  7 purchase totals = $724.63       $766.5626   $766.57   $766.60   $766.60