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	$101.37	9.777%	$111.2809	$111.28	$111.30	$111.30
Purchase #2	$73.88	4.838%	$77.4543	$77.45	$77.45	$77.50
Purchase #3	$176.79	7.706%	$190.4134	$190.41	$190.40	$190.40
Purchase #4	$195.91	6.320%	$208.2915	$208.29	$208.30	$208.30
Purchase #5	$172.32	9.758%	$189.135	$189.14	$189.15	$189.10
Purchase #6	$193.67	7.718%	$208.6175	$208.62	$208.60	$208.60
Purchase #7	$229.51	11.523%	$255.9564	$255.96	$255.95	$256.00
7 purchase totals =	$1,143.45		$1,241.1490	$1,241.15	$1,241.15	$1,241.20