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	$205.57	8.694%	$223.4423	$223.44	$223.45	$223.40
Purchase #2	$241.85	10.418%	$267.0459	$267.05	$267.05	$267.00
Purchase #3	$90.40	9.724%	$99.1905	$99.19	$99.20	$99.20
Purchase #4	$136.83	12.857%	$154.4222	$154.42	$154.40	$154.40
Purchase #5	$50.87	9.561%	$55.7337	$55.73	$55.75	$55.70
Purchase #6	$38.71	10.195%	$42.6565	$42.66	$42.65	$42.70
Purchase #7	$178.45	6.789%	$190.565	$190.57	$190.55	$190.60
7 purchase totals =	$942.68		$1,033.0561	$1,033.06	$1,033.05	$1,033.00