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	$216.83	6.507%	$230.9391	$230.94	$230.95	$230.90
Purchase #2	$172.69	11.529%	$192.5994	$192.60	$192.60	$192.60
Purchase #3	$17.76	13.561%	$20.1684	$20.17	$20.15	$20.20
Purchase #4	$124.41	10.237%	$137.1459	$137.15	$137.15	$137.10
Purchase #5	$79.85	3.694%	$82.7997	$82.80	$82.80	$82.80
Purchase #6	$165.45	11.364%	$184.2517	$184.25	$184.25	$184.30
Purchase #7	$48.64	12.765%	$54.8489	$54.85	$54.85	$54.80
7 purchase totals =	$825.63		$902.7531	$902.76	$902.75	$902.70