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	$105.49	9.317%	$115.3185	$115.32	$115.30	$115.30
Purchase #2	$75.52	13.346%	$85.5989	$85.60	$85.60	$85.60
Purchase #3	$49.32	6.147%	$52.3517	$52.35	$52.35	$52.40
Purchase #4	$39.80	8.113%	$43.029	$43.03	$43.05	$43.00
Purchase #5	$107.33	10.559%	$118.663	$118.66	$118.65	$118.70
Purchase #6	$151.54	5.690%	$160.1626	$160.16	$160.15	$160.20
Purchase #7	$146.52	13.811%	$166.7559	$166.76	$166.75	$166.80
7 purchase totals =	$675.52		$741.8796	$741.88	$741.85	$742.00