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	$225.25	3.761%	$233.7217	$233.72	$233.70	$233.70
Purchase #2	$134.41	5.261%	$141.4813	$141.48	$141.50	$141.50
Purchase #3	$51.32	6.361%	$54.5845	$54.58	$54.60	$54.60
Purchase #4	$57.57	3.523%	$59.5982	$59.60	$59.60	$59.60
Purchase #5	$214.40	9.252%	$234.2363	$234.24	$234.25	$234.20
Purchase #6	$160.47	10.164%	$176.7802	$176.78	$176.80	$176.80
Purchase #7	$8.46	5.383%	$8.9154	$8.92	$8.90	$8.90
7 purchase totals =	$851.88		$909.3176	$909.32	$909.35	$909.30