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	$49.94	9.378%	$54.6234	$54.62	$54.60	$54.60
Purchase #2	$249.49	4.580%	$260.9166	$260.92	$260.90	$260.90
Purchase #3	$237.36	4.419%	$247.8489	$247.85	$247.85	$247.80
Purchase #4	$46.37	10.790%	$51.3733	$51.37	$51.35	$51.40
Purchase #5	$153.59	8.447%	$166.5637	$166.56	$166.55	$166.60
Purchase #6	$117.28	12.125%	$131.5002	$131.50	$131.50	$131.50
Purchase #7	$118.99	7.199%	$127.5561	$127.56	$127.55	$127.60
7 purchase totals =	$973.02		$1,040.3822	$1,040.38	$1,040.30	$1,040.40