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	$128.55	11.647%	$143.5222	$143.52	$143.50	$143.50
Purchase #2	$104.59	4.367%	$109.1574	$109.16	$109.15	$109.20
Purchase #3	$155.30	10.163%	$171.0831	$171.08	$171.10	$171.10
Purchase #4	$178.39	6.562%	$190.096	$190.10	$190.10	$190.10
Purchase #5	$15.32	6.732%	$16.3513	$16.35	$16.35	$16.40
Purchase #6	$113.42	9.250%	$123.9114	$123.91	$123.90	$123.90
Purchase #7	$18.45	11.397%	$20.5527	$20.55	$20.55	$20.60
7 purchase totals =	$714.02		$774.6741	$774.67	$774.65	$774.80