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	$230.37	10.609%	$254.81	$254.81	$254.80	$254.80
Purchase #2	$231.67	12.821%	$261.3724	$261.37	$261.35	$261.40
Purchase #3	$68.42	6.268%	$72.7086	$72.71	$72.70	$72.70
Purchase #4	$118.80	7.637%	$127.8728	$127.87	$127.85	$127.90
Purchase #5	$17.93	5.602%	$18.9344	$18.93	$18.95	$18.90
Purchase #6	$143.44	4.617%	$150.0626	$150.06	$150.05	$150.10
Purchase #7	$78.77	4.291%	$82.15	$82.15	$82.15	$82.20
7 purchase totals =	$889.40		$967.9108	$967.90	$967.85	$968.00