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	$103.92	7.104%	$111.3025	$111.30	$111.30	$111.30
Purchase #2	$113.53	13.289%	$128.617	$128.62	$128.60	$128.60
Purchase #3	$123.26	6.410%	$131.161	$131.16	$131.15	$131.20
Purchase #4	$19.51	10.801%	$21.6173	$21.62	$21.60	$21.60
Purchase #5	$60.92	5.159%	$64.0629	$64.06	$64.05	$64.10
Purchase #6	$47.80	3.423%	$49.4362	$49.44	$49.45	$49.40
Purchase #7	$126.45	13.742%	$143.8268	$143.83	$143.85	$143.80
7 purchase totals =	$595.39		$650.0237	$650.03	$650.00	$650.00