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	$116.59	13.720%	$132.5861	$132.59	$132.60	$132.60
Purchase #2	$145.50	13.200%	$164.706	$164.71	$164.70	$164.70
Purchase #3	$27.52	5.433%	$29.0152	$29.02	$29.00	$29.00
Purchase #4	$31.78	5.399%	$33.4958	$33.50	$33.50	$33.50
Purchase #5	$216.85	13.252%	$245.587	$245.59	$245.60	$245.60
Purchase #6	$73.65	13.202%	$83.3733	$83.37	$83.35	$83.40
Purchase #7	$148.58	6.169%	$157.7459	$157.75	$157.75	$157.70
7 purchase totals =	$760.47		$846.5093	$846.53	$846.50	$846.50