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 $162.76   3.853%   $169.0311   $169.03   $169.05   $169.00  
  Purchase #2 $239.86   11.413%   $267.2352   $267.24   $267.25   $267.20  
  Purchase #3 $34.49   12.126%   $38.6723   $38.67   $38.65   $38.70  
  Purchase #4 $165.50   7.161%   $177.3515   $177.35   $177.35   $177.40  
  Purchase #5 $159.58   9.745%   $175.1311   $175.13   $175.15   $175.10  
  Purchase #6 $211.69   13.352%   $239.9548   $239.95   $239.95   $240.00  
  Purchase #7 $177.86   13.733%   $202.2855   $202.29   $202.30   $202.30  
  7 purchase totals = $1,151.74       $1,269.6615   $1,269.66   $1,269.70   $1,269.70