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	$104.78	6.380%	$111.465	$111.47	$111.45	$111.50
Purchase #2	$88.34	9.823%	$97.0176	$97.02	$97.00	$97.00
Purchase #3	$12.80	3.319%	$13.2248	$13.22	$13.20	$13.20
Purchase #4	$92.77	7.327%	$99.5673	$99.57	$99.55	$99.60
Purchase #5	$212.76	8.235%	$230.2808	$230.28	$230.30	$230.30
Purchase #6	$208.32	12.189%	$233.7121	$233.71	$233.70	$233.70
Purchase #7	$156.73	7.291%	$168.1572	$168.16	$168.15	$168.20
7 purchase totals =	$876.50		$953.4248	$953.43	$953.35	$953.50