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 $224.46   9.756%   $246.3583   $246.36   $246.35   $246.40  
  Purchase #2 $52.92   4.239%   $55.1633   $55.16   $55.15   $55.20  
  Purchase #3 $106.95   6.197%   $113.5777   $113.58   $113.60   $113.60  
  Purchase #4 $235.87   7.122%   $252.6687   $252.67   $252.65   $252.70  
  Purchase #5 $245.75   4.599%   $257.052   $257.05   $257.05   $257.10  
  Purchase #6 $116.67   4.299%   $121.6856   $121.69   $121.70   $121.70  
  Purchase #7 $45.86   6.509%   $48.845   $48.85   $48.85   $48.80  
  7 purchase totals = $1,028.48       $1,095.3506   $1,095.36   $1,095.35   $1,095.50