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	$46.30	9.372%	$50.6392	$50.64	$50.65	$50.60
Purchase #2	$123.75	13.551%	$140.5194	$140.52	$140.50	$140.50
Purchase #3	$216.31	8.810%	$235.3669	$235.37	$235.35	$235.40
Purchase #4	$180.30	11.229%	$200.5459	$200.55	$200.55	$200.50
Purchase #5	$177.77	3.852%	$184.6177	$184.62	$184.60	$184.60
Purchase #6	$44.47	5.397%	$46.87	$46.87	$46.85	$46.90
Purchase #7	$209.67	13.624%	$238.2354	$238.24	$238.25	$238.20
7 purchase totals =	$998.57		$1,096.7945	$1,096.81	$1,096.75	$1,096.70