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	$101.72	9.347%	$111.2278	$111.23	$111.25	$111.20
Purchase #2	$97.60	7.263%	$104.6887	$104.69	$104.70	$104.70
Purchase #3	$66.32	12.103%	$74.3467	$74.35	$74.35	$74.30
Purchase #4	$241.27	10.284%	$266.0822	$266.08	$266.10	$266.10
Purchase #5	$121.99	4.233%	$127.1538	$127.15	$127.15	$127.20
Purchase #6	$147.26	8.819%	$160.2469	$160.25	$160.25	$160.20
Purchase #7	$211.82	4.614%	$221.5934	$221.59	$221.60	$221.60
7 purchase totals =	$987.98		$1,065.3395	$1,065.34	$1,065.40	$1,065.30