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	$42.86	6.382%	$45.5953	$45.60	$45.60	$45.60
Purchase #2	$193.27	6.181%	$205.216	$205.22	$205.20	$205.20
Purchase #3	$59.68	6.569%	$63.6004	$63.60	$63.60	$63.60
Purchase #4	$110.78	5.159%	$116.4951	$116.50	$116.50	$116.50
Purchase #5	$99.56	12.649%	$112.1533	$112.15	$112.15	$112.20
Purchase #6	$29.25	10.770%	$32.4002	$32.40	$32.40	$32.40
Purchase #7	$26.54	6.320%	$28.2173	$28.22	$28.20	$28.20
7 purchase totals =	$561.94		$603.6776	$603.69	$603.65	$603.70