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	$30.87	3.727%	$32.0205	$32.02	$32.00	$32.00
Purchase #2	$17.47	6.379%	$18.5844	$18.58	$18.60	$18.60
Purchase #3	$30.81	7.514%	$33.1251	$33.13	$33.15	$33.10
Purchase #4	$62.36	5.534%	$65.811	$65.81	$65.80	$65.80
Purchase #5	$159.66	5.485%	$168.4174	$168.42	$168.40	$168.40
Purchase #6	$136.37	7.579%	$146.7055	$146.71	$146.70	$146.70
Purchase #7	$19.87	3.592%	$20.5837	$20.58	$20.60	$20.60
7 purchase totals =	$457.41		$485.2476	$485.25	$485.25	$485.20