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 $182.66   12.796%   $206.0332   $206.03   $206.05   $206.00  
  Purchase #2 $185.40   6.579%   $197.5975   $197.60   $197.60   $197.60  
  Purchase #3 $153.75   4.321%   $160.3935   $160.39   $160.40   $160.40  
  Purchase #4 $217.43   8.499%   $235.9094   $235.91   $235.90   $235.90  
  Purchase #5 $96.78   5.822%   $102.4145   $102.41   $102.40   $102.40  
  Purchase #6 $90.95   11.158%   $101.0982   $101.10   $101.10   $101.10  
  Purchase #7 $109.73   4.440%   $114.602   $114.60   $114.60   $114.60  
  7 purchase totals = $1,036.70       $1,118.0483   $1,118.04   $1,118.05   $1,118.00