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	$215.49	8.739%	$234.3217	$234.32	$234.30	$234.30
Purchase #2	$45.99	10.808%	$50.9606	$50.96	$50.95	$51.00
Purchase #3	$48.98	7.326%	$52.5683	$52.57	$52.55	$52.60
Purchase #4	$53.36	12.395%	$59.974	$59.97	$59.95	$60.00
Purchase #5	$221.35	10.426%	$244.428	$244.43	$244.45	$244.40
Purchase #6	$16.59	4.294%	$17.3024	$17.30	$17.30	$17.30
Purchase #7	$53.89	10.371%	$59.4789	$59.48	$59.50	$59.50
7 purchase totals =	$655.65		$719.0339	$719.03	$719.00	$719.10