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 $196.53   7.455%   $211.1813   $211.18   $211.20   $211.20  
  Purchase #2 $48.51   11.116%   $53.9024   $53.90   $53.90   $53.90  
  Purchase #3 $166.77   10.682%   $184.5844   $184.58   $184.60   $184.60  
  Purchase #4 $239.42   3.351%   $247.443   $247.44   $247.45   $247.40  
  Purchase #5 $227.85   13.186%   $257.8943   $257.89   $257.90   $257.90  
  Purchase #6 $47.76   3.833%   $49.5906   $49.59   $49.60   $49.60  
  Purchase #7 $113.61   5.862%   $120.2698   $120.27   $120.25   $120.30  
  7 purchase totals = $1,040.45       $1,124.8658   $1,124.85   $1,124.90   $1,124.90