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	$100.25	4.668%	$104.9297	$104.93	$104.95	$104.90
Purchase #2	$205.28	6.159%	$217.9232	$217.92	$217.90	$217.90
Purchase #3	$14.70	3.761%	$15.2529	$15.25	$15.25	$15.30
Purchase #4	$86.72	13.715%	$98.6136	$98.61	$98.60	$98.60
Purchase #5	$93.63	11.846%	$104.7214	$104.72	$104.70	$104.70
Purchase #6	$141.28	11.845%	$158.0146	$158.01	$158.00	$158.00
Purchase #7	$240.75	9.541%	$263.72	$263.72	$263.70	$263.70
7 purchase totals =	$882.61		$963.1754	$963.16	$963.10	$963.10