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	$163.58	9.220%	$178.6621	$178.66	$178.65	$178.70
Purchase #2	$66.72	10.716%	$73.8697	$73.87	$73.85	$73.90
Purchase #3	$54.66	6.654%	$58.2971	$58.30	$58.30	$58.30
Purchase #4	$86.61	4.595%	$90.5897	$90.59	$90.60	$90.60
Purchase #5	$103.51	12.195%	$116.133	$116.13	$116.15	$116.10
Purchase #6	$69.60	12.125%	$78.039	$78.04	$78.05	$78.00
Purchase #7	$148.34	5.637%	$156.7019	$156.70	$156.70	$156.70
7 purchase totals =	$693.02		$752.2925	$752.29	$752.30	$752.30