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	$98.60	12.661%	$111.0837	$111.08	$111.10	$111.10
Purchase #2	$228.38	10.283%	$251.8643	$251.86	$251.85	$251.90
Purchase #3	$97.51	3.406%	$100.8312	$100.83	$100.85	$100.80
Purchase #4	$146.32	5.592%	$154.5022	$154.50	$154.50	$154.50
Purchase #5	$8.74	13.750%	$9.9418	$9.94	$9.95	$9.90
Purchase #6	$15.49	7.743%	$16.6894	$16.69	$16.70	$16.70
Purchase #7	$172.25	10.552%	$190.4258	$190.43	$190.45	$190.40
7 purchase totals =	$767.29		$835.3384	$835.33	$835.40	$835.30