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	$86.47	4.852%	$90.6655	$90.67	$90.65	$90.70
Purchase #2	$74.35	8.495%	$80.666	$80.67	$80.65	$80.70
Purchase #3	$41.87	4.114%	$43.5925	$43.59	$43.60	$43.60
Purchase #4	$51.49	4.816%	$53.9698	$53.97	$53.95	$54.00
Purchase #5	$51.63	8.663%	$56.1027	$56.10	$56.10	$56.10
Purchase #6	$129.72	10.693%	$143.591	$143.59	$143.60	$143.60
Purchase #7	$17.43	4.739%	$18.256	$18.26	$18.25	$18.30
7 purchase totals =	$452.96		$486.8435	$486.85	$486.80	$487.00