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	$190.36	9.456%	$208.3604	$208.36	$208.35	$208.40
Purchase #2	$172.92	4.491%	$180.6858	$180.69	$180.70	$180.70
Purchase #3	$117.77	5.272%	$123.9788	$123.98	$124.00	$124.00
Purchase #4	$132.94	11.688%	$148.478	$148.48	$148.50	$148.50
Purchase #5	$88.98	12.688%	$100.2698	$100.27	$100.25	$100.30
Purchase #6	$185.89	6.670%	$198.2889	$198.29	$198.30	$198.30
Purchase #7	$166.52	13.772%	$189.4531	$189.45	$189.45	$189.50
7 purchase totals =	$1,055.38		$1,149.5148	$1,149.52	$1,149.55	$1,149.70