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	$155.78	4.246%	$162.3944	$162.39	$162.40	$162.40
Purchase #2	$62.80	4.223%	$65.452	$65.45	$65.45	$65.50
Purchase #3	$132.82	10.479%	$146.7382	$146.74	$146.75	$146.70
Purchase #4	$59.40	13.314%	$67.3085	$67.31	$67.30	$67.30
Purchase #5	$153.42	12.841%	$173.1207	$173.12	$173.10	$173.10
Purchase #6	$156.99	11.768%	$175.4646	$175.46	$175.45	$175.50
Purchase #7	$209.29	13.786%	$238.1427	$238.14	$238.15	$238.10
7 purchase totals =	$930.50		$1,028.6211	$1,028.61	$1,028.60	$1,028.60