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	$49.36	8.259%	$53.4366	$53.44	$53.45	$53.40
Purchase #2	$93.70	8.712%	$101.8631	$101.86	$101.85	$101.90
Purchase #3	$49.81	5.734%	$52.6661	$52.67	$52.65	$52.70
Purchase #4	$28.27	4.512%	$29.5455	$29.55	$29.55	$29.50
Purchase #5	$52.67	13.364%	$59.7088	$59.71	$59.70	$59.70
Purchase #6	$8.35	4.371%	$8.715	$8.72	$8.70	$8.70
Purchase #7	$82.43	9.189%	$90.0045	$90.00	$90.00	$90.00
7 purchase totals =	$364.59		$395.9396	$395.95	$395.90	$395.90