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	$42.26	3.225%	$43.6229	$43.62	$43.60	$43.60
Purchase #2	$196.42	10.708%	$217.4527	$217.45	$217.45	$217.50
Purchase #3	$94.31	7.138%	$101.0418	$101.04	$101.05	$101.00
Purchase #4	$5.76	8.128%	$6.2282	$6.23	$6.25	$6.20
Purchase #5	$103.72	13.524%	$117.7471	$117.75	$117.75	$117.70
Purchase #6	$12.83	5.578%	$13.5457	$13.55	$13.55	$13.50
Purchase #7	$160.30	11.366%	$178.5197	$178.52	$178.50	$178.50
7 purchase totals =	$615.60		$678.1581	$678.16	$678.15	$678.00