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	$78.73	3.431%	$81.4312	$81.43	$81.45	$81.40
Purchase #2	$49.38	6.113%	$52.3986	$52.40	$52.40	$52.40
Purchase #3	$230.66	9.755%	$253.1609	$253.16	$253.15	$253.20
Purchase #4	$7.78	4.167%	$8.1042	$8.10	$8.10	$8.10
Purchase #5	$10.39	10.578%	$11.4891	$11.49	$11.50	$11.50
Purchase #6	$178.35	12.344%	$200.3655	$200.37	$200.35	$200.40
Purchase #7	$96.77	8.592%	$105.0845	$105.08	$105.10	$105.10
7 purchase totals =	$652.06		$712.0340	$712.03	$712.05	$712.10