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	$183.81	6.806%	$196.3201	$196.32	$196.30	$196.30
Purchase #2	$68.28	4.143%	$71.1088	$71.11	$71.10	$71.10
Purchase #3	$19.50	7.845%	$21.0298	$21.03	$21.05	$21.00
Purchase #4	$218.41	5.342%	$230.0775	$230.08	$230.10	$230.10
Purchase #5	$147.44	5.842%	$156.0534	$156.05	$156.05	$156.10
Purchase #6	$48.26	6.719%	$51.5026	$51.50	$51.50	$51.50
Purchase #7	$146.71	8.118%	$158.6199	$158.62	$158.60	$158.60
7 purchase totals =	$832.41		$884.7121	$884.71	$884.70	$884.70