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	$112.99	12.452%	$127.0595	$127.06	$127.05	$127.10
Purchase #2	$30.97	10.373%	$34.1825	$34.18	$34.20	$34.20
Purchase #3	$105.56	10.479%	$116.6216	$116.62	$116.60	$116.60
Purchase #4	$57.54	6.279%	$61.1529	$61.15	$61.15	$61.20
Purchase #5	$89.88	3.382%	$92.9197	$92.92	$92.90	$92.90
Purchase #6	$100.40	11.761%	$112.208	$112.21	$112.20	$112.20
Purchase #7	$231.97	9.302%	$253.5478	$253.55	$253.55	$253.50
7 purchase totals =	$729.31		$797.6920	$797.69	$797.65	$797.70