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	$21.83	9.703%	$23.9482	$23.95	$23.95	$23.90
Purchase #2	$115.37	10.300%	$127.2531	$127.25	$127.25	$127.30
Purchase #3	$81.90	10.712%	$90.6731	$90.67	$90.65	$90.70
Purchase #4	$188.94	6.346%	$200.9301	$200.93	$200.95	$200.90
Purchase #5	$77.74	4.496%	$81.2352	$81.24	$81.25	$81.20
Purchase #6	$59.51	12.710%	$67.0737	$67.07	$67.05	$67.10
Purchase #7	$44.95	5.721%	$47.5216	$47.52	$47.50	$47.50
7 purchase totals =	$590.24		$638.6350	$638.63	$638.60	$638.60