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	$104.80	9.105%	$114.342	$114.34	$114.35	$114.30
Purchase #2	$154.88	5.177%	$162.8981	$162.90	$162.90	$162.90
Purchase #3	$128.40	12.335%	$144.2381	$144.24	$144.25	$144.20
Purchase #4	$120.43	11.169%	$133.8808	$133.88	$133.90	$133.90
Purchase #5	$190.85	12.620%	$214.9353	$214.94	$214.95	$214.90
Purchase #6	$61.33	6.856%	$65.5348	$65.53	$65.55	$65.50
Purchase #7	$22.83	6.481%	$24.3096	$24.31	$24.30	$24.30
7 purchase totals =	$783.52		$860.1387	$860.14	$860.20	$860.00