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	$93.47	6.263%	$99.324	$99.32	$99.30	$99.30
Purchase #2	$172.46	5.156%	$181.352	$181.35	$181.35	$181.40
Purchase #3	$20.80	5.245%	$21.891	$21.89	$21.90	$21.90
Purchase #4	$122.98	8.794%	$133.7949	$133.79	$133.80	$133.80
Purchase #5	$146.27	9.786%	$160.584	$160.58	$160.60	$160.60
Purchase #6	$119.44	6.332%	$127.0029	$127.00	$127.00	$127.00
Purchase #7	$223.25	5.464%	$235.4484	$235.45	$235.45	$235.40
7 purchase totals =	$898.67		$959.3972	$959.38	$959.40	$959.40