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	$49.53	8.181%	$53.582	$53.58	$53.60	$53.60
Purchase #2	$62.58	8.103%	$67.6509	$67.65	$67.65	$67.70
Purchase #3	$21.84	11.692%	$24.3935	$24.39	$24.40	$24.40
Purchase #4	$155.95	4.172%	$162.4562	$162.46	$162.45	$162.50
Purchase #5	$17.60	11.493%	$19.6228	$19.62	$19.60	$19.60
Purchase #6	$81.42	11.482%	$90.7686	$90.77	$90.75	$90.80
Purchase #7	$60.82	9.874%	$66.8254	$66.83	$66.85	$66.80
7 purchase totals =	$449.74		$485.2994	$485.30	$485.30	$485.40