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	$156.61	13.871%	$178.3334	$178.33	$178.35	$178.30
Purchase #2	$131.37	6.845%	$140.3623	$140.36	$140.35	$140.40
Purchase #3	$129.60	9.188%	$141.5076	$141.51	$141.50	$141.50
Purchase #4	$38.49	9.491%	$42.1431	$42.14	$42.15	$42.10
Purchase #5	$41.46	6.126%	$43.9998	$44.00	$44.00	$44.00
Purchase #6	$57.36	8.316%	$62.1301	$62.13	$62.15	$62.10
Purchase #7	$241.72	5.664%	$255.411	$255.41	$255.40	$255.40
7 purchase totals =	$796.61		$863.8873	$863.88	$863.90	$863.80