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 $195.73   11.113%   $217.4815   $217.48   $217.50   $217.50  
  Purchase #2 $169.94   4.189%   $177.0588   $177.06   $177.05   $177.10  
  Purchase #3 $67.53   9.691%   $74.0743   $74.07   $74.05   $74.10  
  Purchase #4 $70.54   5.874%   $74.6835   $74.68   $74.70   $74.70  
  Purchase #5 $69.26   9.770%   $76.0267   $76.03   $76.05   $76.00  
  Purchase #6 $178.42   4.404%   $186.2776   $186.28   $186.30   $186.30  
  Purchase #7 $218.64   10.833%   $242.3253   $242.33   $242.35   $242.30  
  7 purchase totals = $970.06       $1,047.9277   $1,047.93   $1,048.00   $1,048.00