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 $176.90   11.156%   $196.635   $196.64   $196.65   $196.60  
  Purchase #2 $241.58   9.324%   $264.1049   $264.10   $264.10   $264.10  
  Purchase #3 $54.29   3.607%   $56.2482   $56.25   $56.25   $56.20  
  Purchase #4 $229.76   12.571%   $258.6431   $258.64   $258.65   $258.60  
  Purchase #5 $43.64   8.314%   $47.2682   $47.27   $47.25   $47.30  
  Purchase #6 $25.91   4.852%   $27.1672   $27.17   $27.15   $27.20  
  Purchase #7 $41.86   12.109%   $46.9288   $46.93   $46.95   $46.90  
  7 purchase totals = $813.94       $896.9954   $897.00   $897.00   $896.90