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	$230.60	10.748%	$255.3849	$255.38	$255.40	$255.40
Purchase #2	$225.62	7.671%	$242.9273	$242.93	$242.95	$242.90
Purchase #3	$233.41	12.866%	$263.4405	$263.44	$263.45	$263.40
Purchase #4	$105.60	13.478%	$119.8328	$119.83	$119.85	$119.80
Purchase #5	$112.45	13.281%	$127.3845	$127.38	$127.40	$127.40
Purchase #6	$187.90	9.368%	$205.5025	$205.50	$205.50	$205.50
Purchase #7	$82.69	7.319%	$88.7421	$88.74	$88.75	$88.70
7 purchase totals =	$1,178.27		$1,303.2146	$1,303.20	$1,303.30	$1,303.10