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 $85.64   9.248%   $93.56   $93.56   $93.55   $93.60  
  Purchase #2 $208.84   6.742%   $222.92   $222.92   $222.90   $222.90  
  Purchase #3 $150.73   4.590%   $157.6485   $157.65   $157.65   $157.60  
  Purchase #4 $247.81   5.425%   $261.2537   $261.25   $261.25   $261.30  
  Purchase #5 $143.99   6.570%   $153.4501   $153.45   $153.45   $153.50  
  Purchase #6 $10.59   6.507%   $11.2791   $11.28   $11.30   $11.30  
  Purchase #7 $207.33   3.345%   $214.2652   $214.27   $214.25   $214.30  
  7 purchase totals = $1,054.93       $1,114.3766   $1,114.38   $1,114.35   $1,114.50