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 $24.59   5.443%   $25.9284   $25.93   $25.95   $25.90  
  Purchase #2 $120.81   8.195%   $130.7104   $130.71   $130.70   $130.70  
  Purchase #3 $102.92   4.836%   $107.8972   $107.90   $107.90   $107.90  
  Purchase #4 $102.46   4.742%   $107.3187   $107.32   $107.30   $107.30  
  Purchase #5 $53.64   6.534%   $57.1448   $57.14   $57.15   $57.10  
  Purchase #6 $120.76   9.123%   $131.7769   $131.78   $131.80   $131.80  
  Purchase #7 $239.68   5.255%   $252.2752   $252.28   $252.30   $252.30  
  7 purchase totals = $764.86       $813.0516   $813.06   $813.10   $813.00