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	$171.69	5.188%	$180.5973	$180.60	$180.60	$180.60
Purchase #2	$244.93	3.347%	$253.1278	$253.13	$253.15	$253.10
Purchase #3	$50.42	7.333%	$54.1173	$54.12	$54.10	$54.10
Purchase #4	$138.74	7.613%	$149.3023	$149.30	$149.30	$149.30
Purchase #5	$101.64	9.837%	$111.6383	$111.64	$111.65	$111.60
Purchase #6	$127.84	12.642%	$144.0015	$144.00	$144.00	$144.00
Purchase #7	$64.41	10.290%	$71.0378	$71.04	$71.05	$71.00
7 purchase totals =	$899.67		$963.8223	$963.83	$963.85	$963.70