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	$16.77	9.350%	$18.338	$18.34	$18.35	$18.30
Purchase #2	$39.64	9.635%	$43.4593	$43.46	$43.45	$43.50
Purchase #3	$132.40	13.294%	$150.0013	$150.00	$150.00	$150.00
Purchase #4	$238.87	6.825%	$255.1729	$255.17	$255.15	$255.20
Purchase #5	$116.53	9.631%	$127.753	$127.75	$127.75	$127.80
Purchase #6	$19.84	9.147%	$21.6548	$21.65	$21.65	$21.70
Purchase #7	$222.62	12.683%	$250.8549	$250.85	$250.85	$250.90
7 purchase totals =	$786.67		$867.2342	$867.22	$867.20	$867.40