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	$160.76	5.188%	$169.1002	$169.10	$169.10	$169.10
Purchase #2	$72.66	8.143%	$78.5767	$78.58	$78.60	$78.60
Purchase #3	$68.98	8.563%	$74.8868	$74.89	$74.90	$74.90
Purchase #4	$211.61	6.187%	$224.7023	$224.70	$224.70	$224.70
Purchase #5	$194.49	9.237%	$212.455	$212.46	$212.45	$212.50
Purchase #6	$29.71	7.311%	$31.8821	$31.88	$31.90	$31.90
Purchase #7	$104.41	6.628%	$111.3303	$111.33	$111.35	$111.30
7 purchase totals =	$842.62		$902.9334	$902.94	$903.00	$903.00