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	$151.95	5.661%	$160.5519	$160.55	$160.55	$160.60
Purchase #2	$140.29	3.864%	$145.7108	$145.71	$145.70	$145.70
Purchase #3	$59.58	3.431%	$61.6242	$61.62	$61.60	$61.60
Purchase #4	$243.54	11.487%	$271.5154	$271.52	$271.50	$271.50
Purchase #5	$189.32	11.589%	$211.2603	$211.26	$211.25	$211.30
Purchase #6	$173.93	5.295%	$183.1396	$183.14	$183.15	$183.10
Purchase #7	$39.60	4.821%	$41.5091	$41.51	$41.50	$41.50
7 purchase totals =	$998.21		$1,075.3113	$1,075.31	$1,075.25	$1,075.30