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	$127.50	4.861%	$133.6978	$133.70	$133.70	$133.70
Purchase #2	$67.71	4.141%	$70.5139	$70.51	$70.50	$70.50
Purchase #3	$19.80	3.267%	$20.4469	$20.45	$20.45	$20.40
Purchase #4	$211.33	6.796%	$225.692	$225.69	$225.70	$225.70
Purchase #5	$100.50	4.276%	$104.7974	$104.80	$104.80	$104.80
Purchase #6	$65.75	7.354%	$70.5853	$70.59	$70.60	$70.60
Purchase #7	$97.69	7.161%	$104.6856	$104.69	$104.70	$104.70
7 purchase totals =	$690.28		$730.4189	$730.43	$730.45	$730.40