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	$65.60	11.730%	$73.2949	$73.29	$73.30	$73.30
Purchase #2	$19.86	7.741%	$21.3974	$21.40	$21.40	$21.40
Purchase #3	$90.59	5.873%	$95.9104	$95.91	$95.90	$95.90
Purchase #4	$154.53	13.660%	$175.6388	$175.64	$175.65	$175.60
Purchase #5	$127.78	4.341%	$133.3269	$133.33	$133.35	$133.30
Purchase #6	$97.74	5.649%	$103.2613	$103.26	$103.25	$103.30
Purchase #7	$69.92	12.196%	$78.4474	$78.45	$78.45	$78.40
7 purchase totals =	$626.02		$681.2771	$681.28	$681.30	$681.20