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	$85.74	13.105%	$96.9762	$96.98	$97.00	$97.00
Purchase #2	$158.59	13.262%	$179.6222	$179.62	$179.60	$179.60
Purchase #3	$123.64	6.215%	$131.3242	$131.32	$131.30	$131.30
Purchase #4	$35.52	10.669%	$39.3096	$39.31	$39.30	$39.30
Purchase #5	$159.35	8.297%	$172.5713	$172.57	$172.55	$172.60
Purchase #6	$66.66	13.196%	$75.4565	$75.46	$75.45	$75.50
Purchase #7	$217.65	7.730%	$234.4743	$234.47	$234.45	$234.50
7 purchase totals =	$847.15		$929.7343	$929.73	$929.65	$929.80