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 $134.62   9.500%   $147.4089   $147.41   $147.40   $147.40  
  Purchase #2 $247.58   7.402%   $265.9059   $265.91   $265.90   $265.90  
  Purchase #3 $59.53   5.258%   $62.6601   $62.66   $62.65   $62.70  
  Purchase #4 $67.77   9.611%   $74.2834   $74.28   $74.30   $74.30  
  Purchase #5 $206.80   3.299%   $213.6223   $213.62   $213.60   $213.60  
  Purchase #6 $41.81   4.176%   $43.556   $43.56   $43.55   $43.60  
  Purchase #7 $140.61   13.856%   $160.0929   $160.09   $160.10   $160.10  
  7 purchase totals = $898.72       $967.5295   $967.53   $967.50   $967.60