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	$62.68	13.384%	$71.0691	$71.07	$71.05	$71.10
Purchase #2	$159.41	4.538%	$166.644	$166.64	$166.65	$166.60
Purchase #3	$39.94	7.824%	$43.0649	$43.06	$43.05	$43.10
Purchase #4	$195.26	3.171%	$201.4517	$201.45	$201.45	$201.50
Purchase #5	$48.76	10.839%	$54.0451	$54.05	$54.05	$54.00
Purchase #6	$40.49	4.612%	$42.3574	$42.36	$42.35	$42.40
Purchase #7	$106.47	11.415%	$118.6236	$118.62	$118.60	$118.60
7 purchase totals =	$653.01		$697.2558	$697.25	$697.20	$697.30