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	$227.48	10.782%	$252.0069	$252.01	$252.00	$252.00
Purchase #2	$72.98	10.203%	$80.4261	$80.43	$80.45	$80.40
Purchase #3	$237.50	10.457%	$262.3354	$262.34	$262.35	$262.30
Purchase #4	$157.70	7.229%	$169.1001	$169.10	$169.10	$169.10
Purchase #5	$95.45	4.237%	$99.4942	$99.49	$99.50	$99.50
Purchase #6	$159.32	3.194%	$164.4087	$164.41	$164.40	$164.40
Purchase #7	$151.82	13.675%	$172.5814	$172.58	$172.60	$172.60
7 purchase totals =	$1,102.25		$1,200.3528	$1,200.36	$1,200.40	$1,200.30