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	$178.86	13.537%	$203.0723	$203.07	$203.05	$203.10
Purchase #2	$144.60	6.167%	$153.5175	$153.52	$153.50	$153.50
Purchase #3	$54.68	8.110%	$59.1145	$59.11	$59.10	$59.10
Purchase #4	$229.67	10.204%	$253.1055	$253.11	$253.10	$253.10
Purchase #5	$176.38	5.250%	$185.64	$185.64	$185.65	$185.60
Purchase #6	$211.35	9.265%	$230.9316	$230.93	$230.95	$230.90
Purchase #7	$62.69	4.176%	$65.3079	$65.31	$65.30	$65.30
7 purchase totals =	$1,058.23		$1,150.6893	$1,150.69	$1,150.65	$1,150.60