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	$93.52	6.526%	$99.6231	$99.62	$99.60	$99.60
Purchase #2	$248.89	5.159%	$261.7302	$261.73	$261.75	$261.70
Purchase #3	$175.87	10.742%	$194.762	$194.76	$194.75	$194.80
Purchase #4	$230.27	3.282%	$237.8275	$237.83	$237.85	$237.80
Purchase #5	$19.77	8.533%	$21.457	$21.46	$21.45	$21.50
Purchase #6	$120.91	10.808%	$133.978	$133.98	$134.00	$134.00
Purchase #7	$210.50	10.839%	$233.3161	$233.32	$233.30	$233.30
7 purchase totals =	$1,099.73		$1,182.6939	$1,182.70	$1,182.70	$1,182.70