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	$138.87	10.152%	$152.9681	$152.97	$152.95	$153.00
Purchase #2	$11.31	9.605%	$12.3963	$12.40	$12.40	$12.40
Purchase #3	$101.51	9.859%	$111.5179	$111.52	$111.50	$111.50
Purchase #4	$155.81	3.866%	$161.8336	$161.83	$161.85	$161.80
Purchase #5	$6.52	11.676%	$7.2813	$7.28	$7.30	$7.30
Purchase #6	$195.39	13.516%	$221.7989	$221.80	$221.80	$221.80
Purchase #7	$96.47	12.233%	$108.2712	$108.27	$108.25	$108.30
7 purchase totals =	$705.88		$776.0673	$776.07	$776.05	$776.10