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	$9.62	12.130%	$10.7869	$10.79	$10.80	$10.80
Purchase #2	$207.70	5.820%	$219.7881	$219.79	$219.80	$219.80
Purchase #3	$53.33	12.249%	$59.8624	$59.86	$59.85	$59.90
Purchase #4	$78.35	12.863%	$88.4282	$88.43	$88.45	$88.40
Purchase #5	$171.53	9.817%	$188.3691	$188.37	$188.35	$188.40
Purchase #6	$166.53	13.242%	$188.5819	$188.58	$188.60	$188.60
Purchase #7	$6.69	4.698%	$7.0043	$7.00	$7.00	$7.00
7 purchase totals =	$693.75		$762.8209	$762.82	$762.85	$762.90