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 $175.46   12.615%   $197.5943   $197.59   $197.60   $197.60  
  Purchase #2 $175.27   10.293%   $193.3105   $193.31   $193.30   $193.30  
  Purchase #3 $249.51   7.636%   $268.5626   $268.56   $268.55   $268.60  
  Purchase #4 $51.59   6.712%   $55.0527   $55.05   $55.05   $55.10  
  Purchase #5 $153.25   3.501%   $158.6153   $158.62   $158.60   $158.60  
  Purchase #6 $16.35   10.502%   $18.0671   $18.07   $18.05   $18.10  
  Purchase #7 $221.66   5.540%   $233.94   $233.94   $233.95   $233.90  
  7 purchase totals = $1,043.09       $1,125.1425   $1,125.14   $1,125.10   $1,125.20