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	$166.28	7.638%	$178.9805	$178.98	$179.00	$179.00
Purchase #2	$47.97	10.767%	$53.1349	$53.13	$53.15	$53.10
Purchase #3	$198.61	3.687%	$205.9328	$205.93	$205.95	$205.90
Purchase #4	$152.42	9.195%	$166.435	$166.44	$166.45	$166.40
Purchase #5	$57.43	3.522%	$59.4527	$59.45	$59.45	$59.50
Purchase #6	$241.74	6.296%	$256.96	$256.96	$256.95	$257.00
Purchase #7	$45.78	4.171%	$47.6895	$47.69	$47.70	$47.70
7 purchase totals =	$910.23		$968.5854	$968.58	$968.65	$968.60