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	$65.37	9.848%	$71.8076	$71.81	$71.80	$71.80
Purchase #2	$250.88	11.356%	$279.3699	$279.37	$279.35	$279.40
Purchase #3	$97.88	13.693%	$111.2827	$111.28	$111.30	$111.30
Purchase #4	$78.26	3.710%	$81.1634	$81.16	$81.15	$81.20
Purchase #5	$153.51	12.211%	$172.2551	$172.26	$172.25	$172.30
Purchase #6	$231.69	9.338%	$253.3252	$253.33	$253.35	$253.30
Purchase #7	$104.26	12.652%	$117.451	$117.45	$117.45	$117.50
7 purchase totals =	$981.85		$1,086.6549	$1,086.66	$1,086.65	$1,086.80