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	$153.55	8.730%	$166.9549	$166.95	$166.95	$167.00
Purchase #2	$126.76	10.306%	$139.8239	$139.82	$139.80	$139.80
Purchase #3	$100.60	10.788%	$111.4527	$111.45	$111.45	$111.50
Purchase #4	$160.96	7.365%	$172.8147	$172.81	$172.80	$172.80
Purchase #5	$152.77	3.815%	$158.5982	$158.60	$158.60	$158.60
Purchase #6	$115.32	5.743%	$121.9428	$121.94	$121.95	$121.90
Purchase #7	$100.45	8.640%	$109.1289	$109.13	$109.15	$109.10
7 purchase totals =	$910.41		$980.7161	$980.70	$980.70	$980.70