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	$128.72	11.698%	$143.7777	$143.78	$143.80	$143.80
Purchase #2	$190.59	13.554%	$216.4226	$216.42	$216.40	$216.40
Purchase #3	$139.69	4.226%	$145.5933	$145.59	$145.60	$145.60
Purchase #4	$166.78	4.105%	$173.6263	$173.63	$173.65	$173.60
Purchase #5	$178.53	3.865%	$185.4302	$185.43	$185.45	$185.40
Purchase #6	$95.61	9.203%	$104.409	$104.41	$104.40	$104.40
Purchase #7	$38.32	12.868%	$43.251	$43.25	$43.25	$43.30
7 purchase totals =	$938.24		$1,012.5101	$1,012.51	$1,012.55	$1,012.50