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	$158.47	8.868%	$172.5231	$172.52	$172.50	$172.50
Purchase #2	$116.77	5.839%	$123.5882	$123.59	$123.60	$123.60
Purchase #3	$120.92	11.411%	$134.7182	$134.72	$134.70	$134.70
Purchase #4	$117.43	5.749%	$124.1811	$124.18	$124.20	$124.20
Purchase #5	$234.64	13.547%	$266.4267	$266.43	$266.45	$266.40
Purchase #6	$133.88	9.187%	$146.1796	$146.18	$146.20	$146.20
Purchase #7	$72.94	6.218%	$77.4754	$77.48	$77.50	$77.50
7 purchase totals =	$955.05		$1,045.0923	$1,045.10	$1,045.15	$1,045.10