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	$105.32	11.636%	$117.575	$117.58	$117.60	$117.60
Purchase #2	$53.31	3.815%	$55.3438	$55.34	$55.35	$55.30
Purchase #3	$18.75	5.788%	$19.8353	$19.84	$19.85	$19.80
Purchase #4	$87.45	9.557%	$95.8076	$95.81	$95.80	$95.80
Purchase #5	$95.35	4.671%	$99.8038	$99.80	$99.80	$99.80
Purchase #6	$48.75	11.343%	$54.2797	$54.28	$54.30	$54.30
Purchase #7	$145.40	7.371%	$156.1174	$156.12	$156.10	$156.10
7 purchase totals =	$554.33		$598.7626	$598.77	$598.80	$598.70