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	$48.27	7.652%	$51.9636	$51.96	$51.95	$52.00
Purchase #2	$66.78	8.510%	$72.463	$72.46	$72.45	$72.50
Purchase #3	$103.64	7.377%	$111.2855	$111.29	$111.30	$111.30
Purchase #4	$70.83	9.218%	$77.3591	$77.36	$77.35	$77.40
Purchase #5	$124.65	11.729%	$139.2702	$139.27	$139.25	$139.30
Purchase #6	$107.84	9.120%	$117.675	$117.68	$117.70	$117.70
Purchase #7	$241.96	5.737%	$255.8412	$255.84	$255.85	$255.80
7 purchase totals =	$763.97		$825.8576	$825.86	$825.85	$826.00