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	$103.61	11.586%	$115.6143	$115.61	$115.60	$115.60
Purchase #2	$208.55	6.610%	$222.3352	$222.34	$222.35	$222.30
Purchase #3	$48.84	11.483%	$54.4483	$54.45	$54.45	$54.40
Purchase #4	$221.85	3.866%	$230.4267	$230.43	$230.45	$230.40
Purchase #5	$65.38	8.563%	$70.9785	$70.98	$71.00	$71.00
Purchase #6	$178.68	5.265%	$188.0875	$188.09	$188.10	$188.10
Purchase #7	$68.39	6.196%	$72.6274	$72.63	$72.65	$72.60
7 purchase totals =	$895.30		$954.5179	$954.53	$954.60	$954.40