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 $109.44   4.176%   $114.0102   $114.01   $114.00   $114.00  
  Purchase #2 $206.53   5.811%   $218.5315   $218.53   $218.55   $218.50  
  Purchase #3 $81.34   12.691%   $91.6629   $91.66   $91.65   $91.70  
  Purchase #4 $220.72   12.576%   $248.4777   $248.48   $248.50   $248.50  
  Purchase #5 $22.92   10.655%   $25.3621   $25.36   $25.35   $25.40  
  Purchase #6 $247.68   12.746%   $279.2493   $279.25   $279.25   $279.20  
  Purchase #7 $44.35   6.557%   $47.258   $47.26   $47.25   $47.30  
  7 purchase totals = $932.98       $1,024.5517   $1,024.55   $1,024.55   $1,024.60