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	$244.79	4.430%	$255.6342	$255.63	$255.65	$255.60
Purchase #2	$113.77	8.644%	$123.6043	$123.60	$123.60	$123.60
Purchase #3	$233.72	9.710%	$256.4142	$256.41	$256.40	$256.40
Purchase #4	$33.72	12.186%	$37.8291	$37.83	$37.85	$37.80
Purchase #5	$167.81	6.312%	$178.4022	$178.40	$178.40	$178.40
Purchase #6	$47.55	9.536%	$52.0844	$52.08	$52.10	$52.10
Purchase #7	$198.96	4.311%	$207.5372	$207.54	$207.55	$207.50
7 purchase totals =	$1,040.32		$1,111.5056	$1,111.49	$1,111.55	$1,111.40