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	$14.55	10.163%	$16.0287	$16.03	$16.05	$16.00
Purchase #2	$186.50	7.450%	$200.3943	$200.39	$200.40	$200.40
Purchase #3	$244.36	6.308%	$259.7742	$259.77	$259.75	$259.80
Purchase #4	$52.70	13.334%	$59.727	$59.73	$59.75	$59.70
Purchase #5	$64.86	7.667%	$69.8328	$69.83	$69.85	$69.80
Purchase #6	$58.55	4.429%	$61.1432	$61.14	$61.15	$61.10
Purchase #7	$88.78	13.216%	$100.5132	$100.51	$100.50	$100.50
7 purchase totals =	$710.30		$767.4134	$767.40	$767.45	$767.30