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	$110.77	11.798%	$123.8386	$123.84	$123.85	$123.80
Purchase #2	$49.75	11.223%	$55.3334	$55.33	$55.35	$55.30
Purchase #3	$19.43	10.290%	$21.4293	$21.43	$21.45	$21.40
Purchase #4	$238.80	5.595%	$252.1609	$252.16	$252.15	$252.20
Purchase #5	$204.49	9.242%	$223.389	$223.39	$223.40	$223.40
Purchase #6	$151.98	9.378%	$166.2327	$166.23	$166.25	$166.20
Purchase #7	$158.84	8.494%	$172.3319	$172.33	$172.35	$172.30
7 purchase totals =	$934.06		$1,014.7158	$1,014.71	$1,014.80	$1,014.60