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	$200.79	5.573%	$211.98	$211.98	$212.00	$212.00
Purchase #2	$101.98	9.727%	$111.8996	$111.90	$111.90	$111.90
Purchase #3	$185.88	10.240%	$204.9141	$204.91	$204.90	$204.90
Purchase #4	$73.46	13.135%	$83.109	$83.11	$83.10	$83.10
Purchase #5	$222.77	3.378%	$230.2952	$230.30	$230.30	$230.30
Purchase #6	$153.70	12.597%	$173.0616	$173.06	$173.05	$173.10
Purchase #7	$46.43	11.133%	$51.5991	$51.60	$51.60	$51.60
7 purchase totals =	$985.01		$1,066.8586	$1,066.86	$1,066.85	$1,066.90