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	$182.27	4.287%	$190.0839	$190.08	$190.10	$190.10
Purchase #2	$133.52	7.291%	$143.2549	$143.25	$143.25	$143.30
Purchase #3	$203.41	10.127%	$224.0093	$224.01	$224.00	$224.00
Purchase #4	$165.90	4.500%	$173.3655	$173.37	$173.35	$173.40
Purchase #5	$74.61	7.787%	$80.4199	$80.42	$80.40	$80.40
Purchase #6	$124.57	5.825%	$131.8262	$131.83	$131.85	$131.80
Purchase #7	$214.41	5.292%	$225.7566	$225.76	$225.75	$225.80
7 purchase totals =	$1,098.69		$1,168.7163	$1,168.72	$1,168.70	$1,168.80