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	$208.49	12.156%	$233.834	$233.83	$233.85	$233.80
Purchase #2	$100.69	10.790%	$111.5545	$111.55	$111.55	$111.60
Purchase #3	$100.60	11.279%	$111.9467	$111.95	$111.95	$111.90
Purchase #4	$153.41	3.257%	$158.4066	$158.41	$158.40	$158.40
Purchase #5	$113.88	4.259%	$118.7301	$118.73	$118.75	$118.70
Purchase #6	$29.55	5.720%	$31.2403	$31.24	$31.25	$31.20
Purchase #7	$247.68	6.471%	$263.7074	$263.71	$263.70	$263.70
7 purchase totals =	$954.30		$1,029.4196	$1,029.42	$1,029.45	$1,029.30