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	$189.47	5.631%	$200.1391	$200.14	$200.15	$200.10
Purchase #2	$102.55	5.430%	$108.1185	$108.12	$108.10	$108.10
Purchase #3	$118.32	6.103%	$125.5411	$125.54	$125.55	$125.50
Purchase #4	$160.52	7.624%	$172.758	$172.76	$172.75	$172.80
Purchase #5	$59.39	5.478%	$62.6434	$62.64	$62.65	$62.60
Purchase #6	$9.81	10.382%	$10.8285	$10.83	$10.85	$10.80
Purchase #7	$30.58	7.259%	$32.7998	$32.80	$32.80	$32.80
7 purchase totals =	$670.64		$712.8284	$712.83	$712.85	$712.70