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	$97.46	8.373%	$105.6203	$105.62	$105.60	$105.60
Purchase #2	$93.91	12.230%	$105.3952	$105.40	$105.40	$105.40
Purchase #3	$136.50	5.569%	$144.1017	$144.10	$144.10	$144.10
Purchase #4	$173.49	10.388%	$191.5121	$191.51	$191.50	$191.50
Purchase #5	$198.41	13.522%	$225.239	$225.24	$225.25	$225.20
Purchase #6	$77.72	5.699%	$82.1493	$82.15	$82.15	$82.10
Purchase #7	$45.46	5.535%	$47.9762	$47.98	$48.00	$48.00
7 purchase totals =	$822.95		$901.9938	$902.00	$902.00	$901.90