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	$51.75	6.128%	$54.9212	$54.92	$54.90	$54.90
Purchase #2	$198.65	7.729%	$214.0037	$214.00	$214.00	$214.00
Purchase #3	$183.94	11.608%	$205.2918	$205.29	$205.30	$205.30
Purchase #4	$244.85	7.169%	$262.4033	$262.40	$262.40	$262.40
Purchase #5	$35.41	4.540%	$37.0176	$37.02	$37.00	$37.00
Purchase #6	$96.41	6.685%	$102.855	$102.86	$102.85	$102.90
Purchase #7	$100.33	10.767%	$111.1325	$111.13	$111.15	$111.10
7 purchase totals =	$911.34		$987.6251	$987.62	$987.60	$987.60