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	$143.98	7.205%	$154.3538	$154.35	$154.35	$154.40
Purchase #2	$109.60	12.685%	$123.5028	$123.50	$123.50	$123.50
Purchase #3	$230.43	8.654%	$250.3714	$250.37	$250.35	$250.40
Purchase #4	$58.49	6.167%	$62.0971	$62.10	$62.10	$62.10
Purchase #5	$152.72	13.355%	$173.1158	$173.12	$173.10	$173.10
Purchase #6	$221.75	5.839%	$234.698	$234.70	$234.70	$234.70
Purchase #7	$134.73	11.491%	$150.2118	$150.21	$150.20	$150.20
7 purchase totals =	$1,051.70		$1,148.3507	$1,148.35	$1,148.30	$1,148.40