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	$166.96	11.401%	$185.9951	$186.00	$186.00	$186.00
Purchase #2	$191.88	10.415%	$211.8643	$211.86	$211.85	$211.90
Purchase #3	$208.60	11.827%	$233.2711	$233.27	$233.25	$233.30
Purchase #4	$43.76	11.518%	$48.8003	$48.80	$48.80	$48.80
Purchase #5	$186.87	7.296%	$200.504	$200.50	$200.50	$200.50
Purchase #6	$120.65	4.707%	$126.329	$126.33	$126.35	$126.30
Purchase #7	$11.68	12.143%	$13.0983	$13.10	$13.10	$13.10
7 purchase totals =	$930.40		$1,019.8621	$1,019.86	$1,019.85	$1,019.90