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 $72.37   5.689%   $76.4871   $76.49   $76.50   $76.50  
  Purchase #2 $148.91   3.534%   $154.1725   $154.17   $154.15   $154.20  
  Purchase #3 $140.66   5.576%   $148.5032   $148.50   $148.50   $148.50  
  Purchase #4 $237.58   3.289%   $245.394   $245.39   $245.40   $245.40  
  Purchase #5 $132.68   4.784%   $139.0274   $139.03   $139.05   $139.00  
  Purchase #6 $181.47   4.767%   $190.1207   $190.12   $190.10   $190.10  
  Purchase #7 $72.68   12.233%   $81.5709   $81.57   $81.55   $81.60  
  7 purchase totals = $986.35       $1,035.2758   $1,035.27   $1,035.25   $1,035.30