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	$19.57	5.374%	$20.6217	$20.62	$20.60	$20.60
Purchase #2	$50.58	11.300%	$56.2955	$56.30	$56.30	$56.30
Purchase #3	$93.56	6.243%	$99.401	$99.40	$99.40	$99.40
Purchase #4	$189.85	8.385%	$205.7689	$205.77	$205.75	$205.80
Purchase #5	$121.52	5.146%	$127.7734	$127.77	$127.75	$127.80
Purchase #6	$148.35	9.234%	$162.0486	$162.05	$162.05	$162.00
Purchase #7	$173.49	9.610%	$190.1624	$190.16	$190.15	$190.20
7 purchase totals =	$796.92		$862.0715	$862.07	$862.00	$862.10