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	$144.71	10.670%	$160.1506	$160.15	$160.15	$160.20
Purchase #2	$43.73	6.399%	$46.5283	$46.53	$46.55	$46.50
Purchase #3	$57.99	12.147%	$65.034	$65.03	$65.05	$65.00
Purchase #4	$220.89	6.461%	$235.1617	$235.16	$235.15	$235.20
Purchase #5	$63.28	7.233%	$67.857	$67.86	$67.85	$67.90
Purchase #6	$158.45	8.683%	$172.2082	$172.21	$172.20	$172.20
Purchase #7	$197.52	12.685%	$222.5754	$222.58	$222.60	$222.60
7 purchase totals =	$886.57		$969.5152	$969.52	$969.55	$969.60