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	$105.26	8.305%	$114.0018	$114.00	$114.00	$114.00
Purchase #2	$42.30	11.222%	$47.0469	$47.05	$47.05	$47.00
Purchase #3	$166.39	7.466%	$178.8127	$178.81	$178.80	$178.80
Purchase #4	$19.33	10.198%	$21.3013	$21.30	$21.30	$21.30
Purchase #5	$116.68	12.807%	$131.6232	$131.62	$131.60	$131.60
Purchase #6	$178.38	9.492%	$195.3118	$195.31	$195.30	$195.30
Purchase #7	$128.31	6.397%	$136.518	$136.52	$136.50	$136.50
7 purchase totals =	$756.65		$824.6157	$824.61	$824.55	$824.50