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	$52.32	4.465%	$54.6561	$54.66	$54.65	$54.70
Purchase #2	$81.98	12.401%	$92.1463	$92.15	$92.15	$92.10
Purchase #3	$18.53	5.685%	$19.5834	$19.58	$19.60	$19.60
Purchase #4	$164.53	8.720%	$178.877	$178.88	$178.90	$178.90
Purchase #5	$48.30	9.621%	$52.9469	$52.95	$52.95	$52.90
Purchase #6	$152.64	12.866%	$172.2787	$172.28	$172.30	$172.30
Purchase #7	$223.95	6.551%	$238.621	$238.62	$238.60	$238.60
7 purchase totals =	$742.25		$809.1094	$809.12	$809.15	$809.10