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 $167.59   5.391%   $176.6248   $176.62   $176.60   $176.60  
  Purchase #2 $231.80   13.789%   $263.7629   $263.76   $263.75   $263.80  
  Purchase #3 $23.57   11.208%   $26.2117   $26.21   $26.20   $26.20  
  Purchase #4 $52.92   8.280%   $57.3018   $57.30   $57.30   $57.30  
  Purchase #5 $130.86   4.625%   $136.9123   $136.91   $136.90   $136.90  
  Purchase #6 $139.92   9.359%   $153.0151   $153.02   $153.00   $153.00  
  Purchase #7 $225.60   11.131%   $250.7115   $250.71   $250.70   $250.70  
  7 purchase totals = $972.26       $1,064.5401   $1,064.53   $1,064.45   $1,064.50