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 $116.92   8.271%   $126.5905   $126.59   $126.60   $126.60  
  Purchase #2 $174.55   13.828%   $198.6868   $198.69   $198.70   $198.70  
  Purchase #3 $181.84   5.705%   $192.214   $192.21   $192.20   $192.20  
  Purchase #4 $210.65   3.673%   $218.3872   $218.39   $218.40   $218.40  
  Purchase #5 $115.60   3.351%   $119.4738   $119.47   $119.45   $119.50  
  Purchase #6 $208.86   3.848%   $216.8969   $216.90   $216.90   $216.90  
  Purchase #7 $115.86   9.589%   $126.9698   $126.97   $126.95   $127.00  
  7 purchase totals = $1,124.28       $1,199.2190   $1,199.22   $1,199.20   $1,199.30