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	$111.62	13.550%	$126.7445	$126.74	$126.75	$126.70
Purchase #2	$105.99	5.556%	$111.8788	$111.88	$111.90	$111.90
Purchase #3	$163.43	13.460%	$185.4277	$185.43	$185.45	$185.40
Purchase #4	$162.91	6.685%	$173.8005	$173.80	$173.80	$173.80
Purchase #5	$36.63	5.798%	$38.7538	$38.75	$38.75	$38.80
Purchase #6	$51.71	8.829%	$56.2755	$56.28	$56.30	$56.30
Purchase #7	$37.25	5.430%	$39.2727	$39.27	$39.25	$39.30
7 purchase totals =	$669.54		$732.1535	$732.15	$732.20	$732.20