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	$57.44	13.571%	$65.2352	$65.24	$65.25	$65.20
Purchase #2	$74.53	4.217%	$77.6729	$77.67	$77.65	$77.70
Purchase #3	$54.67	9.324%	$59.7674	$59.77	$59.75	$59.80
Purchase #4	$134.60	10.141%	$148.2498	$148.25	$148.25	$148.20
Purchase #5	$240.89	6.308%	$256.0853	$256.09	$256.10	$256.10
Purchase #6	$120.31	6.696%	$128.366	$128.37	$128.35	$128.40
Purchase #7	$123.35	3.434%	$127.5858	$127.59	$127.60	$127.60
7 purchase totals =	$805.79		$862.9624	$862.98	$862.95	$863.00