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	$153.44	8.607%	$166.6466	$166.65	$166.65	$166.60
Purchase #2	$13.29	8.826%	$14.463	$14.46	$14.45	$14.50
Purchase #3	$97.62	11.186%	$108.5398	$108.54	$108.55	$108.50
Purchase #4	$177.34	4.399%	$185.1412	$185.14	$185.15	$185.10
Purchase #5	$96.79	4.105%	$100.7632	$100.76	$100.75	$100.80
Purchase #6	$215.92	6.189%	$229.2833	$229.28	$229.30	$229.30
Purchase #7	$229.72	5.511%	$242.3799	$242.38	$242.40	$242.40
7 purchase totals =	$984.12		$1,047.2170	$1,047.21	$1,047.25	$1,047.20