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	$207.87	12.451%	$233.7519	$233.75	$233.75	$233.80
Purchase #2	$118.63	11.769%	$132.5916	$132.59	$132.60	$132.60
Purchase #3	$55.37	10.357%	$61.1047	$61.10	$61.10	$61.10
Purchase #4	$47.61	4.632%	$49.8153	$49.82	$49.80	$49.80
Purchase #5	$39.85	6.704%	$42.5215	$42.52	$42.50	$42.50
Purchase #6	$83.53	10.266%	$92.1052	$92.11	$92.10	$92.10
Purchase #7	$96.78	11.398%	$107.811	$107.81	$107.80	$107.80
7 purchase totals =	$649.64		$719.7012	$719.70	$719.65	$719.70