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	$216.32	7.738%	$233.0588	$233.06	$233.05	$233.10
Purchase #2	$112.60	13.323%	$127.6017	$127.60	$127.60	$127.60
Purchase #3	$241.82	8.631%	$262.6915	$262.69	$262.70	$262.70
Purchase #4	$247.44	6.290%	$263.004	$263.00	$263.00	$263.00
Purchase #5	$139.73	11.768%	$156.1734	$156.17	$156.15	$156.20
Purchase #6	$67.82	13.152%	$76.7397	$76.74	$76.75	$76.70
Purchase #7	$101.78	9.405%	$111.3524	$111.35	$111.35	$111.40
7 purchase totals =	$1,127.51		$1,230.6215	$1,230.61	$1,230.60	$1,230.70