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	$60.56	10.341%	$66.8225	$66.82	$66.80	$66.80
Purchase #2	$145.39	5.844%	$153.8866	$153.89	$153.90	$153.90
Purchase #3	$241.84	12.671%	$272.4835	$272.48	$272.50	$272.50
Purchase #4	$36.82	11.479%	$41.0466	$41.05	$41.05	$41.00
Purchase #5	$168.38	13.741%	$191.5171	$191.52	$191.50	$191.50
Purchase #6	$74.27	4.329%	$77.4851	$77.49	$77.50	$77.50
Purchase #7	$59.99	8.527%	$65.1053	$65.11	$65.10	$65.10
7 purchase totals =	$787.25		$868.3467	$868.36	$868.35	$868.30