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	$210.42	10.209%	$231.9018	$231.90	$231.90	$231.90
Purchase #2	$160.65	8.615%	$174.49	$174.49	$174.50	$174.50
Purchase #3	$121.52	4.652%	$127.1731	$127.17	$127.15	$127.20
Purchase #4	$205.64	5.565%	$217.0839	$217.08	$217.10	$217.10
Purchase #5	$165.30	4.746%	$173.1451	$173.15	$173.15	$173.10
Purchase #6	$32.98	3.321%	$34.0753	$34.08	$34.10	$34.10
Purchase #7	$90.41	11.476%	$100.7855	$100.79	$100.80	$100.80
7 purchase totals =	$986.92		$1,058.6547	$1,058.66	$1,058.70	$1,058.70