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	$164.56	6.816%	$175.7764	$175.78	$175.80	$175.80
Purchase #2	$161.28	7.344%	$173.1244	$173.12	$173.10	$173.10
Purchase #3	$10.54	3.720%	$10.9321	$10.93	$10.95	$10.90
Purchase #4	$208.97	12.609%	$235.319	$235.32	$235.30	$235.30
Purchase #5	$20.93	5.626%	$22.1075	$22.11	$22.10	$22.10
Purchase #6	$38.52	10.563%	$42.5889	$42.59	$42.60	$42.60
Purchase #7	$49.31	6.316%	$52.4244	$52.42	$52.40	$52.40
7 purchase totals =	$654.11		$712.2727	$712.27	$712.25	$712.20