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	$187.78	10.729%	$207.9269	$207.93	$207.95	$207.90
Purchase #2	$233.43	8.420%	$253.0848	$253.08	$253.10	$253.10
Purchase #3	$131.75	10.845%	$146.0383	$146.04	$146.05	$146.00
Purchase #4	$73.52	9.491%	$80.4978	$80.50	$80.50	$80.50
Purchase #5	$73.29	8.407%	$79.4515	$79.45	$79.45	$79.50
Purchase #6	$173.26	4.806%	$181.5869	$181.59	$181.60	$181.60
Purchase #7	$64.95	9.736%	$71.2735	$71.27	$71.25	$71.30
7 purchase totals =	$937.98		$1,019.8597	$1,019.86	$1,019.90	$1,019.90