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	$94.68	11.551%	$105.6165	$105.62	$105.60	$105.60
Purchase #2	$116.95	10.314%	$129.0122	$129.01	$129.00	$129.00
Purchase #3	$247.91	4.807%	$259.827	$259.83	$259.85	$259.80
Purchase #4	$89.66	11.205%	$99.7064	$99.71	$99.70	$99.70
Purchase #5	$108.66	13.409%	$123.2302	$123.23	$123.25	$123.20
Purchase #6	$89.90	12.226%	$100.8912	$100.89	$100.90	$100.90
Purchase #7	$143.42	10.451%	$158.4088	$158.41	$158.40	$158.40
7 purchase totals =	$891.18		$976.6923	$976.70	$976.70	$976.60