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	$230.46	12.395%	$259.0255	$259.03	$259.05	$259.00
Purchase #2	$184.67	3.348%	$190.8528	$190.85	$190.85	$190.90
Purchase #3	$188.71	8.657%	$205.0466	$205.05	$205.05	$205.00
Purchase #4	$29.73	10.136%	$32.7434	$32.74	$32.75	$32.70
Purchase #5	$176.66	11.465%	$196.9141	$196.91	$196.90	$196.90
Purchase #6	$77.52	10.626%	$85.7573	$85.76	$85.75	$85.80
Purchase #7	$116.27	7.759%	$125.2914	$125.29	$125.30	$125.30
7 purchase totals =	$1,004.02		$1,095.6311	$1,095.63	$1,095.65	$1,095.60