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	$198.88	3.149%	$205.1427	$205.14	$205.15	$205.10
Purchase #2	$69.54	12.258%	$78.0642	$78.06	$78.05	$78.10
Purchase #3	$162.85	7.581%	$175.1957	$175.20	$175.20	$175.20
Purchase #4	$99.82	11.201%	$111.0008	$111.00	$111.00	$111.00
Purchase #5	$12.30	12.229%	$13.8042	$13.80	$13.80	$13.80
Purchase #6	$153.72	5.151%	$161.6381	$161.64	$161.65	$161.60
Purchase #7	$78.74	3.617%	$81.588	$81.59	$81.60	$81.60
7 purchase totals =	$775.85		$826.4337	$826.43	$826.45	$826.40