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	$58.68	11.773%	$65.5884	$65.59	$65.60	$65.60
Purchase #2	$141.83	8.238%	$153.514	$153.51	$153.50	$153.50
Purchase #3	$208.54	9.181%	$227.6861	$227.69	$227.70	$227.70
Purchase #4	$17.94	12.364%	$20.1581	$20.16	$20.15	$20.20
Purchase #5	$181.40	5.461%	$191.3063	$191.31	$191.30	$191.30
Purchase #6	$46.29	7.719%	$49.8631	$49.86	$49.85	$49.90
Purchase #7	$139.57	4.264%	$145.5213	$145.52	$145.50	$145.50
7 purchase totals =	$794.25		$853.6373	$853.64	$853.60	$853.70