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	$212.60	9.663%	$233.1435	$233.14	$233.15	$233.10
Purchase #2	$77.94	11.288%	$86.7379	$86.74	$86.75	$86.70
Purchase #3	$7.25	4.204%	$7.5548	$7.55	$7.55	$7.60
Purchase #4	$230.43	10.842%	$255.4132	$255.41	$255.40	$255.40
Purchase #5	$100.81	3.343%	$104.1801	$104.18	$104.20	$104.20
Purchase #6	$123.25	3.565%	$127.6439	$127.64	$127.65	$127.60
Purchase #7	$86.53	5.711%	$91.4717	$91.47	$91.45	$91.50
7 purchase totals =	$838.81		$906.1451	$906.13	$906.15	$906.10