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	$155.32	7.488%	$166.9504	$166.95	$166.95	$167.00
Purchase #2	$150.44	10.221%	$165.8165	$165.82	$165.80	$165.80
Purchase #3	$100.91	11.304%	$112.3169	$112.32	$112.30	$112.30
Purchase #4	$87.50	7.687%	$94.2261	$94.23	$94.25	$94.20
Purchase #5	$18.93	8.365%	$20.5135	$20.51	$20.50	$20.50
Purchase #6	$211.64	5.868%	$224.059	$224.06	$224.05	$224.10
Purchase #7	$12.49	10.693%	$13.8256	$13.83	$13.85	$13.80
7 purchase totals =	$737.23		$797.7080	$797.72	$797.70	$797.70