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	$212.54	10.531%	$234.9226	$234.92	$234.90	$234.90
Purchase #2	$35.56	7.138%	$38.0983	$38.10	$38.10	$38.10
Purchase #3	$158.98	10.462%	$175.6125	$175.61	$175.60	$175.60
Purchase #4	$74.61	10.408%	$82.3754	$82.38	$82.40	$82.40
Purchase #5	$46.35	10.210%	$51.0823	$51.08	$51.10	$51.10
Purchase #6	$27.58	10.390%	$30.4456	$30.45	$30.45	$30.40
Purchase #7	$107.86	3.452%	$111.5833	$111.58	$111.60	$111.60
7 purchase totals =	$663.48		$724.1200	$724.12	$724.15	$724.10