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	$40.34	3.534%	$41.7656	$41.77	$41.75	$41.80
Purchase #2	$104.39	9.321%	$114.1202	$114.12	$114.10	$114.10
Purchase #3	$52.60	13.391%	$59.6437	$59.64	$59.65	$59.60
Purchase #4	$60.86	10.561%	$67.2874	$67.29	$67.30	$67.30
Purchase #5	$235.40	8.301%	$254.9406	$254.94	$254.95	$254.90
Purchase #6	$138.78	5.504%	$146.4185	$146.42	$146.40	$146.40
Purchase #7	$37.29	7.649%	$40.1423	$40.14	$40.15	$40.10
7 purchase totals =	$669.66		$724.3183	$724.32	$724.30	$724.20