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 $218.67   3.698%   $226.7564   $226.76   $226.75   $226.80  
  Purchase #2 $100.92   13.290%   $114.3323   $114.33   $114.35   $114.30  
  Purchase #3 $178.66   3.302%   $184.5594   $184.56   $184.55   $184.60  
  Purchase #4 $89.67   9.702%   $98.3698   $98.37   $98.35   $98.40  
  Purchase #5 $93.54   9.509%   $102.4347   $102.43   $102.45   $102.40  
  Purchase #6 $164.61   8.286%   $178.2496   $178.25   $178.25   $178.20  
  Purchase #7 $186.58   6.728%   $199.1331   $199.13   $199.15   $199.10  
  7 purchase totals = $1,032.65       $1,103.8353   $1,103.83   $1,103.85   $1,103.80