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	$6.33	11.479%	$7.0566	$7.06	$7.05	$7.10
Purchase #2	$39.44	3.663%	$40.8847	$40.88	$40.90	$40.90
Purchase #3	$197.56	5.164%	$207.762	$207.76	$207.75	$207.80
Purchase #4	$119.52	6.773%	$127.6151	$127.62	$127.60	$127.60
Purchase #5	$121.43	5.125%	$127.6533	$127.65	$127.65	$127.70
Purchase #6	$92.64	8.311%	$100.3393	$100.34	$100.35	$100.30
Purchase #7	$170.27	8.533%	$184.7991	$184.80	$184.80	$184.80
7 purchase totals =	$747.19		$796.1101	$796.11	$796.10	$796.20