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	$105.28	10.757%	$116.605	$116.61	$116.60	$116.60
Purchase #2	$196.71	13.112%	$222.5026	$222.50	$222.50	$222.50
Purchase #3	$159.38	3.163%	$164.4212	$164.42	$164.40	$164.40
Purchase #4	$191.65	7.299%	$205.6385	$205.64	$205.65	$205.60
Purchase #5	$71.49	8.141%	$77.31	$77.31	$77.30	$77.30
Purchase #6	$168.97	5.103%	$177.5925	$177.59	$177.60	$177.60
Purchase #7	$137.60	11.365%	$153.2382	$153.24	$153.25	$153.20
7 purchase totals =	$1,031.08		$1,117.3080	$1,117.31	$1,117.30	$1,117.20