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	$77.70	13.845%	$88.4576	$88.46	$88.45	$88.50
Purchase #2	$77.86	5.324%	$82.0053	$82.01	$82.00	$82.00
Purchase #3	$124.60	3.156%	$128.5324	$128.53	$128.55	$128.50
Purchase #4	$35.31	8.378%	$38.2683	$38.27	$38.25	$38.30
Purchase #5	$145.29	13.867%	$165.4374	$165.44	$165.45	$165.40
Purchase #6	$39.83	10.109%	$43.8564	$43.86	$43.85	$43.90
Purchase #7	$103.40	10.690%	$114.4535	$114.45	$114.45	$114.50
7 purchase totals =	$603.99		$661.0109	$661.02	$661.00	$661.10