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	$71.43	8.333%	$77.3823	$77.38	$77.40	$77.40
Purchase #2	$142.39	8.445%	$154.4148	$154.41	$154.40	$154.40
Purchase #3	$138.52	12.472%	$155.7962	$155.80	$155.80	$155.80
Purchase #4	$51.39	4.206%	$53.5515	$53.55	$53.55	$53.60
Purchase #5	$34.82	10.237%	$38.3845	$38.38	$38.40	$38.40
Purchase #6	$227.87	4.851%	$238.924	$238.92	$238.90	$238.90
Purchase #7	$50.92	11.688%	$56.8715	$56.87	$56.85	$56.90
7 purchase totals =	$717.34		$775.3248	$775.31	$775.30	$775.40