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	$108.72	8.201%	$117.6361	$117.64	$117.65	$117.60
Purchase #2	$25.48	10.151%	$28.0665	$28.07	$28.05	$28.10
Purchase #3	$153.46	13.116%	$173.5878	$173.59	$173.60	$173.60
Purchase #4	$233.85	13.440%	$265.2794	$265.28	$265.30	$265.30
Purchase #5	$104.36	5.277%	$109.8671	$109.87	$109.85	$109.90
Purchase #6	$222.85	7.150%	$238.7838	$238.78	$238.80	$238.80
Purchase #7	$202.54	9.399%	$221.5767	$221.58	$221.60	$221.60
7 purchase totals =	$1,051.26		$1,154.7974	$1,154.81	$1,154.85	$1,154.90