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	$98.92	12.852%	$111.6332	$111.63	$111.65	$111.60
Purchase #2	$108.39	12.656%	$122.1078	$122.11	$122.10	$122.10
Purchase #3	$157.84	10.716%	$174.7541	$174.75	$174.75	$174.80
Purchase #4	$230.29	4.805%	$241.3554	$241.36	$241.35	$241.40
Purchase #5	$119.86	6.169%	$127.2542	$127.25	$127.25	$127.30
Purchase #6	$124.78	5.668%	$131.8525	$131.85	$131.85	$131.90
Purchase #7	$154.62	9.443%	$169.2208	$169.22	$169.20	$169.20
7 purchase totals =	$994.70		$1,078.1780	$1,078.17	$1,078.15	$1,078.30