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	$68.82	6.721%	$73.4454	$73.45	$73.45	$73.40
Purchase #2	$34.46	10.589%	$38.109	$38.11	$38.10	$38.10
Purchase #3	$188.38	8.552%	$204.4903	$204.49	$204.50	$204.50
Purchase #4	$52.46	8.857%	$57.1064	$57.11	$57.10	$57.10
Purchase #5	$122.75	3.494%	$127.0389	$127.04	$127.05	$127.00
Purchase #6	$107.58	3.342%	$111.1753	$111.18	$111.20	$111.20
Purchase #7	$99.67	3.397%	$103.0558	$103.06	$103.05	$103.10
7 purchase totals =	$674.12		$714.4211	$714.44	$714.45	$714.40