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	$152.65	13.255%	$172.8838	$172.88	$172.90	$172.90
Purchase #2	$44.37	8.108%	$47.9675	$47.97	$47.95	$48.00
Purchase #3	$173.52	4.551%	$181.4169	$181.42	$181.40	$181.40
Purchase #4	$83.71	5.833%	$88.5928	$88.59	$88.60	$88.60
Purchase #5	$154.26	12.106%	$172.9347	$172.93	$172.95	$172.90
Purchase #6	$239.52	9.831%	$263.0672	$263.07	$263.05	$263.10
Purchase #7	$81.75	13.480%	$92.7699	$92.77	$92.75	$92.80
7 purchase totals =	$929.78		$1,019.6328	$1,019.63	$1,019.60	$1,019.70