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	$161.25	4.511%	$168.524	$168.52	$168.50	$168.50
Purchase #2	$227.37	6.213%	$241.4965	$241.50	$241.50	$241.50
Purchase #3	$146.68	4.493%	$153.2703	$153.27	$153.25	$153.30
Purchase #4	$59.80	3.353%	$61.8051	$61.81	$61.80	$61.80
Purchase #5	$208.26	12.128%	$233.5178	$233.52	$233.50	$233.50
Purchase #6	$139.80	9.545%	$153.1439	$153.14	$153.15	$153.10
Purchase #7	$117.53	3.453%	$121.5883	$121.59	$121.60	$121.60
7 purchase totals =	$1,060.69		$1,133.3459	$1,133.35	$1,133.30	$1,133.30