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 $68.80   10.449%   $75.9889   $75.99   $76.00   $76.00  
  Purchase #2 $111.44   13.337%   $126.3028   $126.30   $126.30   $126.30  
  Purchase #3 $43.89   3.873%   $45.5899   $45.59   $45.60   $45.60  
  Purchase #4 $153.59   4.328%   $160.2374   $160.24   $160.25   $160.20  
  Purchase #5 $111.42   4.813%   $116.7826   $116.78   $116.80   $116.80  
  Purchase #6 $232.61   12.571%   $261.8514   $261.85   $261.85   $261.90  
  Purchase #7 $250.89   10.105%   $276.2424   $276.24   $276.25   $276.20  
  7 purchase totals = $972.64       $1,062.9954   $1,062.99   $1,063.05   $1,063.00