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	$247.38	7.448%	$265.8049	$265.80	$265.80	$265.80
Purchase #2	$144.62	10.849%	$160.3098	$160.31	$160.30	$160.30
Purchase #3	$130.84	7.784%	$141.0246	$141.02	$141.00	$141.00
Purchase #4	$222.29	3.874%	$230.9015	$230.90	$230.90	$230.90
Purchase #5	$146.45	8.245%	$158.5248	$158.52	$158.50	$158.50
Purchase #6	$148.76	10.362%	$164.1745	$164.17	$164.15	$164.20
Purchase #7	$102.38	6.166%	$108.6928	$108.69	$108.70	$108.70
7 purchase totals =	$1,142.72		$1,229.4329	$1,229.41	$1,229.35	$1,229.40