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	$221.70	8.294%	$240.0878	$240.09	$240.10	$240.10
Purchase #2	$70.98	10.501%	$78.4336	$78.43	$78.45	$78.40
Purchase #3	$48.43	3.695%	$50.2195	$50.22	$50.20	$50.20
Purchase #4	$156.80	3.142%	$161.7267	$161.73	$161.75	$161.70
Purchase #5	$230.80	11.115%	$256.4534	$256.45	$256.45	$256.50
Purchase #6	$208.34	12.695%	$234.7888	$234.79	$234.80	$234.80
Purchase #7	$74.51	12.170%	$83.5779	$83.58	$83.60	$83.60
7 purchase totals =	$1,011.56		$1,105.2877	$1,105.29	$1,105.35	$1,105.30