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	$125.92	8.495%	$136.6169	$136.62	$136.60	$136.60
Purchase #2	$247.78	11.658%	$276.6662	$276.67	$276.65	$276.70
Purchase #3	$200.70	5.393%	$211.5238	$211.52	$211.50	$211.50
Purchase #4	$119.70	10.460%	$132.2206	$132.22	$132.20	$132.20
Purchase #5	$80.32	6.114%	$85.2308	$85.23	$85.25	$85.20
Purchase #6	$59.33	11.149%	$65.9447	$65.94	$65.95	$65.90
Purchase #7	$103.72	4.867%	$108.7681	$108.77	$108.75	$108.80
7 purchase totals =	$937.47		$1,016.9711	$1,016.97	$1,016.90	$1,016.90