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	$49.61	9.702%	$54.4232	$54.42	$54.40	$54.40
Purchase #2	$102.52	8.423%	$111.1553	$111.16	$111.15	$111.20
Purchase #3	$159.64	9.363%	$174.5871	$174.59	$174.60	$174.60
Purchase #4	$37.31	10.644%	$41.2813	$41.28	$41.30	$41.30
Purchase #5	$143.80	3.147%	$148.3254	$148.33	$148.35	$148.30
Purchase #6	$167.65	13.187%	$189.758	$189.76	$189.75	$189.80
Purchase #7	$230.69	13.244%	$261.2426	$261.24	$261.25	$261.20
7 purchase totals =	$891.22		$980.7729	$980.78	$980.80	$980.80