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	$106.61	12.176%	$119.5908	$119.59	$119.60	$119.60
Purchase #2	$196.86	13.177%	$222.8002	$222.80	$222.80	$222.80
Purchase #3	$110.28	10.702%	$122.0822	$122.08	$122.10	$122.10
Purchase #4	$37.87	5.284%	$39.8711	$39.87	$39.85	$39.90
Purchase #5	$49.52	9.800%	$54.373	$54.37	$54.35	$54.40
Purchase #6	$145.83	5.420%	$153.734	$153.73	$153.75	$153.70
Purchase #7	$20.25	5.219%	$21.3068	$21.31	$21.30	$21.30
7 purchase totals =	$667.22		$733.7581	$733.75	$733.75	$733.80