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	$42.77	5.801%	$45.2511	$45.25	$45.25	$45.30
Purchase #2	$35.61	10.570%	$39.374	$39.37	$39.35	$39.40
Purchase #3	$212.52	7.779%	$229.0519	$229.05	$229.05	$229.10
Purchase #4	$20.50	6.631%	$21.8594	$21.86	$21.85	$21.90
Purchase #5	$230.78	4.626%	$241.4559	$241.46	$241.45	$241.50
Purchase #6	$112.96	13.503%	$128.213	$128.21	$128.20	$128.20
Purchase #7	$35.28	11.867%	$39.4667	$39.47	$39.45	$39.50
7 purchase totals =	$690.42		$744.6720	$744.67	$744.60	$744.90