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	$49.26	8.848%	$53.6185	$53.62	$53.60	$53.60
Purchase #2	$47.98	7.743%	$51.6951	$51.70	$51.70	$51.70
Purchase #3	$123.60	6.783%	$131.9838	$131.98	$132.00	$132.00
Purchase #4	$62.63	8.397%	$67.889	$67.89	$67.90	$67.90
Purchase #5	$29.89	10.129%	$32.9176	$32.92	$32.90	$32.90
Purchase #6	$206.52	13.388%	$234.1689	$234.17	$234.15	$234.20
Purchase #7	$71.92	10.681%	$79.6018	$79.60	$79.60	$79.60
7 purchase totals =	$591.80		$651.8747	$651.88	$651.85	$651.90