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	$166.35	4.499%	$173.8341	$173.83	$173.85	$173.80
Purchase #2	$26.93	8.621%	$29.2516	$29.25	$29.25	$29.30
Purchase #3	$245.48	10.348%	$270.8823	$270.88	$270.90	$270.90
Purchase #4	$154.98	12.170%	$173.8411	$173.84	$173.85	$173.80
Purchase #5	$118.56	7.525%	$127.4816	$127.48	$127.50	$127.50
Purchase #6	$214.62	11.188%	$238.6317	$238.63	$238.65	$238.60
Purchase #7	$140.35	12.850%	$158.385	$158.39	$158.40	$158.40
7 purchase totals =	$1,067.27		$1,172.3074	$1,172.30	$1,172.40	$1,172.30