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	$125.74	11.231%	$139.8619	$139.86	$139.85	$139.90
Purchase #2	$169.67	3.391%	$175.4235	$175.42	$175.40	$175.40
Purchase #3	$168.74	12.773%	$190.2932	$190.29	$190.30	$190.30
Purchase #4	$46.60	6.216%	$49.4967	$49.50	$49.50	$49.50
Purchase #5	$40.41	6.718%	$43.1247	$43.12	$43.10	$43.10
Purchase #6	$8.87	6.677%	$9.4622	$9.46	$9.45	$9.50
Purchase #7	$101.49	10.302%	$111.9455	$111.95	$111.95	$111.90
7 purchase totals =	$661.52		$719.6077	$719.60	$719.55	$719.60