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	$240.81	10.679%	$266.5261	$266.53	$266.55	$266.50
Purchase #2	$222.72	8.231%	$241.0521	$241.05	$241.05	$241.10
Purchase #3	$40.26	12.574%	$45.3223	$45.32	$45.30	$45.30
Purchase #4	$129.65	10.769%	$143.612	$143.61	$143.60	$143.60
Purchase #5	$98.96	12.320%	$111.1519	$111.15	$111.15	$111.20
Purchase #6	$93.54	7.785%	$100.8221	$100.82	$100.80	$100.80
Purchase #7	$230.79	4.430%	$241.014	$241.01	$241.00	$241.00
7 purchase totals =	$1,056.73		$1,149.5005	$1,149.49	$1,149.45	$1,149.50