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	$124.93	13.345%	$141.6019	$141.60	$141.60	$141.60
Purchase #2	$106.86	11.163%	$118.7888	$118.79	$118.80	$118.80
Purchase #3	$20.40	7.262%	$21.8814	$21.88	$21.90	$21.90
Purchase #4	$86.91	3.244%	$89.7294	$89.73	$89.75	$89.70
Purchase #5	$225.56	8.492%	$244.7146	$244.71	$244.70	$244.70
Purchase #6	$167.93	11.741%	$187.6467	$187.65	$187.65	$187.60
Purchase #7	$148.51	5.105%	$156.0914	$156.09	$156.10	$156.10
7 purchase totals =	$881.10		$960.4542	$960.45	$960.50	$960.40