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	$238.90	6.162%	$253.621	$253.62	$253.60	$253.60
Purchase #2	$215.33	6.793%	$229.9574	$229.96	$229.95	$230.00
Purchase #3	$220.84	8.611%	$239.8565	$239.86	$239.85	$239.90
Purchase #4	$198.52	7.835%	$214.074	$214.07	$214.05	$214.10
Purchase #5	$15.83	11.255%	$17.6117	$17.61	$17.60	$17.60
Purchase #6	$110.91	6.862%	$118.5206	$118.52	$118.50	$118.50
Purchase #7	$83.58	8.746%	$90.8899	$90.89	$90.90	$90.90
7 purchase totals =	$1,083.91		$1,164.5311	$1,164.53	$1,164.45	$1,164.60