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	$23.92	7.532%	$25.7217	$25.72	$25.70	$25.70
Purchase #2	$65.85	10.546%	$72.7945	$72.79	$72.80	$72.80
Purchase #3	$25.62	6.715%	$27.3404	$27.34	$27.35	$27.30
Purchase #4	$127.69	11.346%	$142.1777	$142.18	$142.20	$142.20
Purchase #5	$19.60	11.773%	$21.9075	$21.91	$21.90	$21.90
Purchase #6	$163.89	8.663%	$178.0878	$178.09	$178.10	$178.10
Purchase #7	$111.35	6.148%	$118.1958	$118.20	$118.20	$118.20
7 purchase totals =	$537.92		$586.2254	$586.23	$586.25	$586.20