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	$68.97	4.772%	$72.2612	$72.26	$72.25	$72.30
Purchase #2	$110.87	11.195%	$123.2819	$123.28	$123.30	$123.30
Purchase #3	$104.86	6.117%	$111.2743	$111.27	$111.25	$111.30
Purchase #4	$210.80	9.176%	$230.143	$230.14	$230.15	$230.10
Purchase #5	$209.51	12.136%	$234.9361	$234.94	$234.95	$234.90
Purchase #6	$5.32	5.152%	$5.5941	$5.59	$5.60	$5.60
Purchase #7	$120.79	13.246%	$136.7898	$136.79	$136.80	$136.80
7 purchase totals =	$831.12		$914.2804	$914.27	$914.30	$914.30