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 $58.44   7.120%   $62.6009   $62.60   $62.60   $62.60  
  Purchase #2 $68.99   7.414%   $74.1049   $74.10   $74.10   $74.10  
  Purchase #3 $174.78   8.726%   $190.0313   $190.03   $190.05   $190.00  
  Purchase #4 $89.43   10.245%   $98.5921   $98.59   $98.60   $98.60  
  Purchase #5 $206.77   10.116%   $227.6869   $227.69   $227.70   $227.70  
  Purchase #6 $179.88   5.785%   $190.2861   $190.29   $190.30   $190.30  
  Purchase #7 $70.64   7.461%   $75.9105   $75.91   $75.90   $75.90  
  7 purchase totals = $848.93       $919.2127   $919.21   $919.25   $919.20