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	$136.56	7.357%	$146.6067	$146.61	$146.60	$146.60
Purchase #2	$49.45	3.680%	$51.2698	$51.27	$51.25	$51.30
Purchase #3	$9.77	10.714%	$10.8168	$10.82	$10.80	$10.80
Purchase #4	$177.64	4.871%	$186.2928	$186.29	$186.30	$186.30
Purchase #5	$90.43	13.783%	$102.894	$102.89	$102.90	$102.90
Purchase #6	$95.65	4.673%	$100.1197	$100.12	$100.10	$100.10
Purchase #7	$105.31	8.633%	$114.4014	$114.40	$114.40	$114.40
7 purchase totals =	$664.81		$712.4012	$712.40	$712.35	$712.40