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	$215.75	10.834%	$239.1244	$239.12	$239.10	$239.10
Purchase #2	$28.94	11.518%	$32.2733	$32.27	$32.25	$32.30
Purchase #3	$237.37	12.229%	$266.398	$266.40	$266.40	$266.40
Purchase #4	$118.90	4.514%	$124.2671	$124.27	$124.25	$124.30
Purchase #5	$136.82	8.607%	$148.5961	$148.60	$148.60	$148.60
Purchase #6	$126.91	13.305%	$143.7954	$143.80	$143.80	$143.80
Purchase #7	$238.91	12.419%	$268.5802	$268.58	$268.60	$268.60
7 purchase totals =	$1,103.60		$1,223.0345	$1,223.04	$1,223.00	$1,223.10