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	$93.95	13.671%	$106.7939	$106.79	$106.80	$106.80
Purchase #2	$194.67	11.340%	$216.7456	$216.75	$216.75	$216.70
Purchase #3	$112.49	13.436%	$127.6042	$127.60	$127.60	$127.60
Purchase #4	$151.96	4.478%	$158.7648	$158.76	$158.75	$158.80
Purchase #5	$119.53	6.327%	$127.0927	$127.09	$127.10	$127.10
Purchase #6	$139.32	4.559%	$145.6716	$145.67	$145.65	$145.70
Purchase #7	$185.40	7.771%	$199.8074	$199.81	$199.80	$199.80
7 purchase totals =	$997.32		$1,082.4802	$1,082.47	$1,082.45	$1,082.50