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	$74.64	11.692%	$83.3669	$83.37	$83.35	$83.40
Purchase #2	$19.27	12.298%	$21.6398	$21.64	$21.65	$21.60
Purchase #3	$162.74	4.621%	$170.2602	$170.26	$170.25	$170.30
Purchase #4	$148.52	12.356%	$166.8711	$166.87	$166.85	$166.90
Purchase #5	$8.87	13.382%	$10.057	$10.06	$10.05	$10.10
Purchase #6	$244.74	12.542%	$275.4353	$275.44	$275.45	$275.40
Purchase #7	$89.26	12.712%	$100.6067	$100.61	$100.60	$100.60
7 purchase totals =	$748.04		$828.2370	$828.25	$828.20	$828.30