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	$166.45	4.422%	$173.8104	$173.81	$173.80	$173.80
Purchase #2	$247.80	5.796%	$262.1625	$262.16	$262.15	$262.20
Purchase #3	$122.32	4.521%	$127.8501	$127.85	$127.85	$127.90
Purchase #4	$204.59	12.695%	$230.5627	$230.56	$230.55	$230.60
Purchase #5	$224.93	7.373%	$241.5141	$241.51	$241.50	$241.50
Purchase #6	$189.34	3.173%	$195.3478	$195.35	$195.35	$195.30
Purchase #7	$230.43	4.844%	$241.592	$241.59	$241.60	$241.60
7 purchase totals =	$1,385.86		$1,472.8396	$1,472.83	$1,472.80	$1,472.90