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	$230.29	5.691%	$243.3958	$243.40	$243.40	$243.40
Purchase #2	$38.82	5.152%	$40.82	$40.82	$40.80	$40.80
Purchase #3	$46.30	13.729%	$52.6565	$52.66	$52.65	$52.70
Purchase #4	$60.37	11.701%	$67.4339	$67.43	$67.45	$67.40
Purchase #5	$118.78	11.619%	$132.581	$132.58	$132.60	$132.60
Purchase #6	$249.33	11.491%	$277.9805	$277.98	$278.00	$278.00
Purchase #7	$71.90	11.534%	$80.1929	$80.19	$80.20	$80.20
7 purchase totals =	$815.79		$895.0606	$895.06	$895.10	$895.10