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	$151.46	7.500%	$162.8195	$162.82	$162.80	$162.80
Purchase #2	$95.54	5.759%	$101.0421	$101.04	$101.05	$101.00
Purchase #3	$210.82	9.294%	$230.4136	$230.41	$230.40	$230.40
Purchase #4	$112.42	12.839%	$126.8536	$126.85	$126.85	$126.90
Purchase #5	$144.52	12.377%	$162.4072	$162.41	$162.40	$162.40
Purchase #6	$52.75	4.448%	$55.0963	$55.10	$55.10	$55.10
Purchase #7	$127.83	3.679%	$132.5329	$132.53	$132.55	$132.50
7 purchase totals =	$895.34		$971.1652	$971.16	$971.15	$971.10