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	$153.64	12.109%	$172.2443	$172.24	$172.25	$172.20
Purchase #2	$191.38	4.808%	$200.5816	$200.58	$200.60	$200.60
Purchase #3	$8.32	13.483%	$9.4418	$9.44	$9.45	$9.40
Purchase #4	$249.57	4.611%	$261.0777	$261.08	$261.10	$261.10
Purchase #5	$82.79	9.644%	$90.7743	$90.77	$90.75	$90.80
Purchase #6	$64.65	11.416%	$72.0304	$72.03	$72.05	$72.00
Purchase #7	$126.50	6.442%	$134.6491	$134.65	$134.65	$134.60
7 purchase totals =	$876.85		$940.7992	$940.79	$940.85	$940.70