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	$60.80	7.552%	$65.3916	$65.39	$65.40	$65.40
Purchase #2	$62.66	5.158%	$65.892	$65.89	$65.90	$65.90
Purchase #3	$118.74	12.511%	$133.5956	$133.60	$133.60	$133.60
Purchase #4	$106.65	4.125%	$111.0493	$111.05	$111.05	$111.00
Purchase #5	$18.38	11.481%	$20.4902	$20.49	$20.50	$20.50
Purchase #6	$42.52	8.746%	$46.2388	$46.24	$46.25	$46.20
Purchase #7	$32.53	4.269%	$33.9187	$33.92	$33.90	$33.90
7 purchase totals =	$442.28		$476.5762	$476.58	$476.60	$476.50