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	$82.62	9.286%	$90.2921	$90.29	$90.30	$90.30
Purchase #2	$21.93	11.436%	$24.4379	$24.44	$24.45	$24.40
Purchase #3	$108.29	4.246%	$112.888	$112.89	$112.90	$112.90
Purchase #4	$26.64	4.482%	$27.834	$27.83	$27.85	$27.80
Purchase #5	$249.90	11.375%	$278.3261	$278.33	$278.35	$278.30
Purchase #6	$239.72	6.583%	$255.5008	$255.50	$255.50	$255.50
Purchase #7	$47.81	9.388%	$52.2984	$52.30	$52.30	$52.30
7 purchase totals =	$776.91		$841.5773	$841.58	$841.65	$841.50