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	$143.69	10.491%	$158.7645	$158.76	$158.75	$158.80
Purchase #2	$48.42	10.522%	$53.5148	$53.51	$53.50	$53.50
Purchase #3	$155.37	8.825%	$169.0814	$169.08	$169.10	$169.10
Purchase #4	$250.35	3.545%	$259.2249	$259.22	$259.20	$259.20
Purchase #5	$123.36	11.139%	$137.1011	$137.10	$137.10	$137.10
Purchase #6	$206.98	12.856%	$233.5893	$233.59	$233.60	$233.60
Purchase #7	$103.58	11.852%	$115.8563	$115.86	$115.85	$115.90
7 purchase totals =	$1,031.75		$1,127.1323	$1,127.12	$1,127.10	$1,127.20