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 $245.34   7.508%   $263.7601   $263.76   $263.75   $263.80  
  Purchase #2 $229.39   12.781%   $258.7083   $258.71   $258.70   $258.70  
  Purchase #3 $168.95   12.550%   $190.1532   $190.15   $190.15   $190.20  
  Purchase #4 $151.91   5.476%   $160.2286   $160.23   $160.25   $160.20  
  Purchase #5 $44.43   12.793%   $50.1139   $50.11   $50.10   $50.10  
  Purchase #6 $44.99   5.292%   $47.3709   $47.37   $47.35   $47.40  
  Purchase #7 $38.75   12.624%   $43.6418   $43.64   $43.65   $43.60  
  7 purchase totals = $923.76       $1,013.9768   $1,013.97   $1,013.95   $1,014.00