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	$160.47	11.805%	$179.4135	$179.41	$179.40	$179.40
Purchase #2	$42.29	3.768%	$43.8835	$43.88	$43.90	$43.90
Purchase #3	$45.89	4.298%	$47.8624	$47.86	$47.85	$47.90
Purchase #4	$15.40	11.242%	$17.1313	$17.13	$17.15	$17.10
Purchase #5	$109.28	8.301%	$118.3513	$118.35	$118.35	$118.40
Purchase #6	$138.53	5.818%	$146.5897	$146.59	$146.60	$146.60
Purchase #7	$47.31	12.589%	$53.2659	$53.27	$53.25	$53.30
7 purchase totals =	$559.17		$606.4976	$606.49	$606.50	$606.60