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 $246.35   8.370%   $266.9695   $266.97   $266.95   $267.00  
  Purchase #2 $82.96   8.509%   $90.0191   $90.02   $90.00   $90.00  
  Purchase #3 $131.51   8.788%   $143.0671   $143.07   $143.05   $143.10  
  Purchase #4 $222.84   8.467%   $241.7079   $241.71   $241.70   $241.70  
  Purchase #5 $105.97   8.213%   $114.6733   $114.67   $114.65   $114.70  
  Purchase #6 $114.90   3.734%   $119.1904   $119.19   $119.20   $119.20  
  Purchase #7 $128.56   4.498%   $134.3426   $134.34   $134.35   $134.30  
  7 purchase totals = $1,033.09       $1,109.9699   $1,109.97   $1,109.90   $1,110.00