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	$211.53	12.176%	$237.2859	$237.29	$237.30	$237.30
Purchase #2	$19.72	6.117%	$20.9263	$20.93	$20.95	$20.90
Purchase #3	$33.71	12.490%	$37.9204	$37.92	$37.90	$37.90
Purchase #4	$37.43	8.119%	$40.4689	$40.47	$40.45	$40.50
Purchase #5	$176.28	3.844%	$183.0562	$183.06	$183.05	$183.10
Purchase #6	$146.57	5.401%	$154.4862	$154.49	$154.50	$154.50
Purchase #7	$108.31	5.665%	$114.4458	$114.45	$114.45	$114.40
7 purchase totals =	$733.55		$788.5897	$788.61	$788.60	$788.60