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	$97.96	5.734%	$103.577	$103.58	$103.60	$103.60
Purchase #2	$144.83	4.284%	$151.0345	$151.03	$151.05	$151.00
Purchase #3	$156.40	11.142%	$173.8261	$173.83	$173.85	$173.80
Purchase #4	$238.71	6.835%	$255.0258	$255.03	$255.05	$255.00
Purchase #5	$19.67	12.162%	$22.0623	$22.06	$22.05	$22.10
Purchase #6	$66.28	11.793%	$74.0964	$74.10	$74.10	$74.10
Purchase #7	$222.74	7.869%	$240.2674	$240.27	$240.25	$240.30
7 purchase totals =	$946.59		$1,019.8895	$1,019.90	$1,019.95	$1,019.90