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	$89.92	10.685%	$99.528	$99.53	$99.55	$99.50
Purchase #2	$108.41	13.131%	$122.6453	$122.65	$122.65	$122.60
Purchase #3	$190.28	7.628%	$204.7946	$204.79	$204.80	$204.80
Purchase #4	$112.44	13.376%	$127.48	$127.48	$127.50	$127.50
Purchase #5	$249.97	13.410%	$283.491	$283.49	$283.50	$283.50
Purchase #6	$117.61	12.683%	$132.5265	$132.53	$132.55	$132.50
Purchase #7	$148.96	11.545%	$166.1574	$166.16	$166.15	$166.20
7 purchase totals =	$1,017.59		$1,136.6228	$1,136.63	$1,136.70	$1,136.60