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	$233.64	11.308%	$260.06	$260.06	$260.05	$260.10
Purchase #2	$233.51	11.418%	$260.1722	$260.17	$260.15	$260.20
Purchase #3	$66.74	7.478%	$71.7308	$71.73	$71.75	$71.70
Purchase #4	$45.89	13.131%	$51.9158	$51.92	$51.90	$51.90
Purchase #5	$33.83	9.609%	$37.0807	$37.08	$37.10	$37.10
Purchase #6	$87.42	3.669%	$90.6274	$90.63	$90.65	$90.60
Purchase #7	$55.52	5.378%	$58.5059	$58.51	$58.50	$58.50
7 purchase totals =	$756.55		$830.0928	$830.10	$830.10	$830.10