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	$39.58	9.609%	$43.3832	$43.38	$43.40	$43.40
Purchase #2	$145.49	4.378%	$151.8596	$151.86	$151.85	$151.90
Purchase #3	$10.46	11.433%	$11.6559	$11.66	$11.65	$11.70
Purchase #4	$45.30	3.852%	$47.045	$47.05	$47.05	$47.00
Purchase #5	$33.91	3.607%	$35.1331	$35.13	$35.15	$35.10
Purchase #6	$111.76	10.206%	$123.1662	$123.17	$123.15	$123.20
Purchase #7	$52.29	12.848%	$59.0082	$59.01	$59.00	$59.00
7 purchase totals =	$438.79		$471.2512	$471.26	$471.25	$471.30