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	$244.56	7.720%	$263.44	$263.44	$263.45	$263.40
Purchase #2	$84.42	5.748%	$89.2725	$89.27	$89.25	$89.30
Purchase #3	$126.89	4.660%	$132.8031	$132.80	$132.80	$132.80
Purchase #4	$153.59	8.151%	$166.1091	$166.11	$166.10	$166.10
Purchase #5	$149.77	6.594%	$159.6458	$159.65	$159.65	$159.60
Purchase #6	$32.55	6.813%	$34.7676	$34.77	$34.75	$34.80
Purchase #7	$164.42	5.125%	$172.8465	$172.85	$172.85	$172.80
7 purchase totals =	$956.20		$1,018.8846	$1,018.89	$1,018.85	$1,018.80