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	$216.79	9.137%	$236.5981	$236.60	$236.60	$236.60
Purchase #2	$153.95	7.559%	$165.5871	$165.59	$165.60	$165.60
Purchase #3	$107.72	3.301%	$111.2758	$111.28	$111.30	$111.30
Purchase #4	$167.66	6.672%	$178.8463	$178.85	$178.85	$178.80
Purchase #5	$202.34	11.179%	$224.9596	$224.96	$224.95	$225.00
Purchase #6	$205.61	12.133%	$230.5567	$230.56	$230.55	$230.60
Purchase #7	$142.55	11.345%	$158.7223	$158.72	$158.70	$158.70
7 purchase totals =	$1,196.62		$1,306.5459	$1,306.56	$1,306.55	$1,306.60