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	$246.70	3.566%	$255.4973	$255.50	$255.50	$255.50
Purchase #2	$141.43	12.142%	$158.6024	$158.60	$158.60	$158.60
Purchase #3	$177.81	6.560%	$189.4743	$189.47	$189.45	$189.50
Purchase #4	$99.48	13.274%	$112.685	$112.69	$112.70	$112.70
Purchase #5	$214.81	10.146%	$236.6046	$236.60	$236.60	$236.60
Purchase #6	$57.40	13.723%	$65.277	$65.28	$65.30	$65.30
Purchase #7	$194.29	9.302%	$212.3629	$212.36	$212.35	$212.40
7 purchase totals =	$1,131.92		$1,230.5035	$1,230.50	$1,230.50	$1,230.60