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	$151.77	9.786%	$166.6222	$166.62	$166.60	$166.60
Purchase #2	$44.42	9.651%	$48.707	$48.71	$48.70	$48.70
Purchase #3	$226.92	4.585%	$237.3243	$237.32	$237.30	$237.30
Purchase #4	$126.84	8.543%	$137.6759	$137.68	$137.70	$137.70
Purchase #5	$86.55	3.655%	$89.7134	$89.71	$89.70	$89.70
Purchase #6	$207.89	12.104%	$233.053	$233.05	$233.05	$233.10
Purchase #7	$210.30	6.260%	$223.4648	$223.46	$223.45	$223.50
7 purchase totals =	$1,054.69		$1,136.5606	$1,136.55	$1,136.50	$1,136.60