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 $60.27   12.412%   $67.7507   $67.75   $67.75   $67.80  
  Purchase #2 $241.39   8.345%   $261.534   $261.53   $261.55   $261.50  
  Purchase #3 $168.76   9.178%   $184.2488   $184.25   $184.25   $184.20  
  Purchase #4 $86.64   11.742%   $96.8133   $96.81   $96.80   $96.80  
  Purchase #5 $32.30   11.168%   $35.9073   $35.91   $35.90   $35.90  
  Purchase #6 $161.71   11.484%   $180.2808   $180.28   $180.30   $180.30  
  Purchase #7 $46.69   4.225%   $48.6627   $48.66   $48.65   $48.70  
  7 purchase totals = $797.76       $875.1976   $875.19   $875.20   $875.20