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	$77.58	13.644%	$88.165	$88.17	$88.15	$88.20
Purchase #2	$9.98	6.462%	$10.6249	$10.62	$10.60	$10.60
Purchase #3	$48.97	13.810%	$55.7328	$55.73	$55.75	$55.70
Purchase #4	$200.64	8.351%	$217.3954	$217.40	$217.40	$217.40
Purchase #5	$174.89	13.297%	$198.1451	$198.15	$198.15	$198.10
Purchase #6	$140.76	10.442%	$155.4582	$155.46	$155.45	$155.50
Purchase #7	$127.83	11.105%	$142.0255	$142.03	$142.05	$142.00
7 purchase totals =	$780.65		$867.5469	$867.56	$867.55	$867.50