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	$208.52	8.808%	$226.8864	$226.89	$226.90	$226.90
Purchase #2	$219.73	9.440%	$240.4725	$240.47	$240.45	$240.50
Purchase #3	$32.79	13.715%	$37.2871	$37.29	$37.30	$37.30
Purchase #4	$143.44	10.610%	$158.659	$158.66	$158.65	$158.70
Purchase #5	$112.71	3.534%	$116.6932	$116.69	$116.70	$116.70
Purchase #6	$235.58	13.404%	$267.1571	$267.16	$267.15	$267.20
Purchase #7	$198.86	8.353%	$215.4708	$215.47	$215.45	$215.50
7 purchase totals =	$1,151.63		$1,262.6261	$1,262.63	$1,262.60	$1,262.80