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	$9.86	6.112%	$10.4626	$10.46	$10.45	$10.50
Purchase #2	$28.63	12.105%	$32.0957	$32.10	$32.10	$32.10
Purchase #3	$80.55	12.575%	$90.6792	$90.68	$90.70	$90.70
Purchase #4	$30.43	12.179%	$34.1361	$34.14	$34.15	$34.10
Purchase #5	$140.42	7.519%	$150.9782	$150.98	$151.00	$151.00
Purchase #6	$42.67	12.579%	$48.0375	$48.04	$48.05	$48.00
Purchase #7	$224.82	3.766%	$233.2867	$233.29	$233.30	$233.30
7 purchase totals =	$557.38		$599.6760	$599.69	$599.75	$599.70