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	$227.92	4.435%	$238.0283	$238.03	$238.05	$238.00
Purchase #2	$214.72	3.580%	$222.407	$222.41	$222.40	$222.40
Purchase #3	$155.75	10.688%	$172.3966	$172.40	$172.40	$172.40
Purchase #4	$249.28	9.703%	$273.4676	$273.47	$273.45	$273.50
Purchase #5	$130.75	11.133%	$145.3064	$145.31	$145.30	$145.30
Purchase #6	$244.54	9.131%	$266.8689	$266.87	$266.85	$266.90
Purchase #7	$145.84	3.594%	$151.0815	$151.08	$151.10	$151.10
7 purchase totals =	$1,368.80		$1,469.5563	$1,469.57	$1,469.55	$1,469.60