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	$160.39	4.105%	$166.974	$166.97	$166.95	$167.00
Purchase #2	$54.81	12.251%	$61.5248	$61.52	$61.50	$61.50
Purchase #3	$140.38	5.703%	$148.3859	$148.39	$148.40	$148.40
Purchase #4	$226.31	3.223%	$233.604	$233.60	$233.60	$233.60
Purchase #5	$36.90	3.733%	$38.2775	$38.28	$38.30	$38.30
Purchase #6	$224.38	4.200%	$233.804	$233.80	$233.80	$233.80
Purchase #7	$13.42	3.122%	$13.839	$13.84	$13.85	$13.80
7 purchase totals =	$856.59		$896.4092	$896.40	$896.40	$896.40