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 $104.82   9.132%   $114.3922   $114.39   $114.40   $114.40  
  Purchase #2 $22.92   5.323%   $24.14   $24.14   $24.15   $24.10  
  Purchase #3 $40.96   10.571%   $45.2899   $45.29   $45.30   $45.30  
  Purchase #4 $96.31   8.391%   $104.3914   $104.39   $104.40   $104.40  
  Purchase #5 $47.95   3.685%   $49.717   $49.72   $49.70   $49.70  
  Purchase #6 $53.80   7.433%   $57.799   $57.80   $57.80   $57.80  
  Purchase #7 $202.49   4.503%   $211.6081   $211.61   $211.60   $211.60  
  7 purchase totals = $569.25       $607.3376   $607.34   $607.35   $607.30