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	$64.51	12.510%	$72.5802	$72.58	$72.60	$72.60
Purchase #2	$92.99	8.362%	$100.7658	$100.77	$100.75	$100.80
Purchase #3	$128.91	3.163%	$132.9874	$132.99	$133.00	$133.00
Purchase #4	$58.91	13.153%	$66.6584	$66.66	$66.65	$66.70
Purchase #5	$166.45	4.647%	$174.1849	$174.18	$174.20	$174.20
Purchase #6	$159.98	5.333%	$168.5117	$168.51	$168.50	$168.50
Purchase #7	$152.41	5.696%	$161.0913	$161.09	$161.10	$161.10
7 purchase totals =	$824.16		$876.7797	$876.78	$876.80	$876.90