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	$229.36	10.865%	$254.28	$254.28	$254.30	$254.30
Purchase #2	$36.90	3.253%	$38.1004	$38.10	$38.10	$38.10
Purchase #3	$127.43	7.319%	$136.7566	$136.76	$136.75	$136.80
Purchase #4	$102.68	8.565%	$111.4745	$111.47	$111.45	$111.50
Purchase #5	$132.25	10.735%	$146.447	$146.45	$146.45	$146.40
Purchase #6	$39.97	4.516%	$41.775	$41.78	$41.80	$41.80
Purchase #7	$157.98	5.336%	$166.4098	$166.41	$166.40	$166.40
7 purchase totals =	$826.57		$895.2433	$895.25	$895.25	$895.30