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 $104.64   9.299%   $114.3705   $114.37   $114.35   $114.40  
  Purchase #2 $209.91   3.649%   $217.5696   $217.57   $217.55   $217.60  
  Purchase #3 $189.80   7.448%   $203.9363   $203.94   $203.95   $203.90  
  Purchase #4 $193.96   6.337%   $206.2512   $206.25   $206.25   $206.30  
  Purchase #5 $143.53   8.338%   $155.4975   $155.50   $155.50   $155.50  
  Purchase #6 $247.84   4.706%   $259.5034   $259.50   $259.50   $259.50  
  Purchase #7 $11.77   4.174%   $12.2613   $12.26   $12.25   $12.30  
  7 purchase totals = $1,101.45       $1,169.3898   $1,169.39   $1,169.35   $1,169.50