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 $95.53   13.716%   $108.6329   $108.63   $108.65   $108.60  
  Purchase #2 $242.48   7.756%   $261.2867   $261.29   $261.30   $261.30  
  Purchase #3 $156.27   4.644%   $163.5272   $163.53   $163.55   $163.50  
  Purchase #4 $211.53   12.793%   $238.591   $238.59   $238.60   $238.60  
  Purchase #5 $166.30   5.716%   $175.8057   $175.81   $175.80   $175.80  
  Purchase #6 $114.84   3.844%   $119.2544   $119.25   $119.25   $119.30  
  Purchase #7 $140.92   13.713%   $160.2444   $160.24   $160.25   $160.20  
  7 purchase totals = $1,127.87       $1,227.3423   $1,227.34   $1,227.40   $1,227.30