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	$183.70	13.647%	$208.7695	$208.77	$208.75	$208.80
Purchase #2	$14.43	7.599%	$15.5265	$15.53	$15.55	$15.50
Purchase #3	$18.62	12.146%	$20.8816	$20.88	$20.90	$20.90
Purchase #4	$59.67	11.510%	$66.538	$66.54	$66.55	$66.50
Purchase #5	$72.90	9.383%	$79.7402	$79.74	$79.75	$79.70
Purchase #6	$188.43	12.419%	$211.8311	$211.83	$211.85	$211.80
Purchase #7	$100.83	10.396%	$111.3123	$111.31	$111.30	$111.30
7 purchase totals =	$638.58		$714.5992	$714.60	$714.65	$714.50