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	$119.74	6.183%	$127.1435	$127.14	$127.15	$127.10
Purchase #2	$200.98	11.342%	$223.7752	$223.78	$223.80	$223.80
Purchase #3	$191.52	12.293%	$215.0636	$215.06	$215.05	$215.10
Purchase #4	$18.38	13.365%	$20.8365	$20.84	$20.85	$20.80
Purchase #5	$205.72	3.213%	$212.3298	$212.33	$212.35	$212.30
Purchase #6	$52.46	7.856%	$56.5813	$56.58	$56.60	$56.60
Purchase #7	$228.99	5.514%	$241.6165	$241.62	$241.60	$241.60
7 purchase totals =	$1,017.79		$1,097.3464	$1,097.35	$1,097.40	$1,097.30