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	$178.48	11.420%	$198.8624	$198.86	$198.85	$198.90
Purchase #2	$158.45	5.333%	$166.9001	$166.90	$166.90	$166.90
Purchase #3	$51.32	8.833%	$55.8531	$55.85	$55.85	$55.90
Purchase #4	$219.34	8.836%	$238.7209	$238.72	$238.70	$238.70
Purchase #5	$10.30	4.479%	$10.7613	$10.76	$10.75	$10.80
Purchase #6	$56.66	3.395%	$58.5836	$58.58	$58.60	$58.60
Purchase #7	$150.88	6.863%	$161.2349	$161.23	$161.25	$161.20
7 purchase totals =	$825.43		$890.9163	$890.90	$890.90	$891.00