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	$40.93	12.758%	$46.1518	$46.15	$46.15	$46.20
Purchase #2	$191.52	4.685%	$200.4927	$200.49	$200.50	$200.50
Purchase #3	$158.75	4.766%	$166.316	$166.32	$166.30	$166.30
Purchase #4	$167.44	3.559%	$173.3992	$173.40	$173.40	$173.40
Purchase #5	$138.80	5.122%	$145.9093	$145.91	$145.90	$145.90
Purchase #6	$242.28	3.753%	$251.3728	$251.37	$251.35	$251.40
Purchase #7	$60.69	11.584%	$67.7203	$67.72	$67.70	$67.70
7 purchase totals =	$1,000.41		$1,051.3621	$1,051.36	$1,051.30	$1,051.40