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	$42.60	6.813%	$45.5023	$45.50	$45.50	$45.50
Purchase #2	$5.98	11.509%	$6.6682	$6.67	$6.65	$6.70
Purchase #3	$56.97	4.301%	$59.4203	$59.42	$59.40	$59.40
Purchase #4	$165.93	3.740%	$172.1358	$172.14	$172.15	$172.10
Purchase #5	$88.48	4.273%	$92.2608	$92.26	$92.25	$92.30
Purchase #6	$96.28	8.559%	$104.5206	$104.52	$104.50	$104.50
Purchase #7	$219.30	5.601%	$231.583	$231.58	$231.60	$231.60
7 purchase totals =	$675.54		$712.0910	$712.09	$712.05	$712.10