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	$228.99	4.156%	$238.5068	$238.51	$238.50	$238.50
Purchase #2	$228.39	4.539%	$238.7566	$238.76	$238.75	$238.80
Purchase #3	$117.73	7.754%	$126.8588	$126.86	$126.85	$126.90
Purchase #4	$151.59	7.735%	$163.3155	$163.32	$163.30	$163.30
Purchase #5	$90.32	8.773%	$98.2438	$98.24	$98.25	$98.20
Purchase #6	$105.45	10.352%	$116.3662	$116.37	$116.35	$116.40
Purchase #7	$250.85	11.570%	$279.8733	$279.87	$279.85	$279.90
7 purchase totals =	$1,173.32		$1,261.9210	$1,261.93	$1,261.85	$1,262.00