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	$93.34	8.704%	$101.4643	$101.46	$101.45	$101.50
Purchase #2	$49.92	13.291%	$56.5549	$56.55	$56.55	$56.60
Purchase #3	$54.97	13.571%	$62.43	$62.43	$62.45	$62.40
Purchase #4	$43.25	12.221%	$48.5356	$48.54	$48.55	$48.50
Purchase #5	$199.78	10.191%	$220.1396	$220.14	$220.15	$220.10
Purchase #6	$36.26	3.255%	$37.4403	$37.44	$37.45	$37.40
Purchase #7	$57.85	8.204%	$62.596	$62.60	$62.60	$62.60
7 purchase totals =	$535.37		$589.1607	$589.16	$589.20	$589.10