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	$119.43	3.137%	$123.1765	$123.18	$123.20	$123.20
Purchase #2	$74.79	13.843%	$85.1432	$85.14	$85.15	$85.10
Purchase #3	$133.83	13.575%	$151.9974	$152.00	$152.00	$152.00
Purchase #4	$49.58	8.136%	$53.6138	$53.61	$53.60	$53.60
Purchase #5	$24.56	13.420%	$27.856	$27.86	$27.85	$27.90
Purchase #6	$121.83	13.504%	$138.2819	$138.28	$138.30	$138.30
Purchase #7	$169.85	3.713%	$176.1565	$176.16	$176.15	$176.20
7 purchase totals =	$693.87		$756.2253	$756.23	$756.25	$756.30