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	$41.57	3.433%	$42.9971	$43.00	$43.00	$43.00
Purchase #2	$11.52	8.826%	$12.5368	$12.54	$12.55	$12.50
Purchase #3	$138.25	12.482%	$155.5064	$155.51	$155.50	$155.50
Purchase #4	$157.39	11.256%	$175.1058	$175.11	$175.10	$175.10
Purchase #5	$55.99	9.332%	$61.215	$61.22	$61.20	$61.20
Purchase #6	$155.77	11.126%	$173.101	$173.10	$173.10	$173.10
Purchase #7	$50.94	13.735%	$57.9366	$57.94	$57.95	$57.90
7 purchase totals =	$611.43		$678.3987	$678.42	$678.40	$678.30