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	$87.53	10.570%	$96.7819	$96.78	$96.80	$96.80
Purchase #2	$112.29	13.869%	$127.8635	$127.86	$127.85	$127.90
Purchase #3	$106.43	11.391%	$118.5534	$118.55	$118.55	$118.60
Purchase #4	$158.92	10.730%	$175.9721	$175.97	$175.95	$176.00
Purchase #5	$110.32	12.667%	$124.2942	$124.29	$124.30	$124.30
Purchase #6	$48.75	10.416%	$53.8278	$53.83	$53.85	$53.80
Purchase #7	$99.82	8.508%	$108.3127	$108.31	$108.30	$108.30
7 purchase totals =	$724.06		$805.6056	$805.59	$805.60	$805.70