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 $239.76   9.545%   $262.6451   $262.65   $262.65   $262.60  
  Purchase #2 $115.82   8.111%   $125.2142   $125.21   $125.20   $125.20  
  Purchase #3 $173.91   9.515%   $190.4575   $190.46   $190.45   $190.50  
  Purchase #4 $211.86   13.322%   $240.084   $240.08   $240.10   $240.10  
  Purchase #5 $145.30   5.351%   $153.075   $153.08   $153.10   $153.10  
  Purchase #6 $134.76   13.392%   $152.8071   $152.81   $152.80   $152.80  
  Purchase #7 $33.63   12.108%   $37.7019   $37.70   $37.70   $37.70  
  7 purchase totals = $1,055.04       $1,161.9848   $1,161.99   $1,162.00   $1,162.00