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	$108.38	7.136%	$116.114	$116.11	$116.10	$116.10
Purchase #2	$89.62	4.366%	$93.5328	$93.53	$93.55	$93.50
Purchase #3	$130.88	10.467%	$144.5792	$144.58	$144.60	$144.60
Purchase #4	$81.51	10.600%	$90.1501	$90.15	$90.15	$90.20
Purchase #5	$43.78	10.668%	$48.4505	$48.45	$48.45	$48.50
Purchase #6	$157.61	8.678%	$171.2874	$171.29	$171.30	$171.30
Purchase #7	$185.28	8.454%	$200.9436	$200.94	$200.95	$200.90
7 purchase totals =	$797.06		$865.0576	$865.05	$865.10	$865.10