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	$146.49	5.312%	$154.2715	$154.27	$154.25	$154.30
Purchase #2	$220.77	10.800%	$244.6132	$244.61	$244.60	$244.60
Purchase #3	$141.39	8.732%	$153.7362	$153.74	$153.75	$153.70
Purchase #4	$108.66	13.195%	$122.9977	$123.00	$123.00	$123.00
Purchase #5	$57.33	9.175%	$62.59	$62.59	$62.60	$62.60
Purchase #6	$211.32	12.651%	$238.0541	$238.05	$238.05	$238.10
Purchase #7	$105.99	7.174%	$113.5937	$113.59	$113.60	$113.60
7 purchase totals =	$991.95		$1,089.8564	$1,089.85	$1,089.85	$1,089.90