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	$240.59	7.771%	$259.2862	$259.29	$259.30	$259.30
Purchase #2	$17.88	3.340%	$18.4772	$18.48	$18.50	$18.50
Purchase #3	$128.51	13.212%	$145.4887	$145.49	$145.50	$145.50
Purchase #4	$20.87	9.350%	$22.8213	$22.82	$22.80	$22.80
Purchase #5	$15.96	13.814%	$18.1647	$18.16	$18.15	$18.20
Purchase #6	$176.85	6.229%	$187.866	$187.87	$187.85	$187.90
Purchase #7	$42.86	10.287%	$47.269	$47.27	$47.25	$47.30
7 purchase totals =	$643.52		$699.3731	$699.38	$699.35	$699.50