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 $114.67   3.799%   $119.0263   $119.03   $119.05   $119.00  
  Purchase #2 $60.53   3.762%   $62.8071   $62.81   $62.80   $62.80  
  Purchase #3 $87.65   8.599%   $95.187   $95.19   $95.20   $95.20  
  Purchase #4 $15.50   5.675%   $16.3796   $16.38   $16.40   $16.40  
  Purchase #5 $189.40   3.750%   $196.5025   $196.50   $196.50   $196.50  
  Purchase #6 $136.45   6.856%   $145.805   $145.81   $145.80   $145.80  
  Purchase #7 $109.62   7.364%   $117.6924   $117.69   $117.70   $117.70  
  7 purchase totals = $713.82       $753.3999   $753.41   $753.45   $753.40