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	$69.81	3.308%	$72.1193	$72.12	$72.10	$72.10
Purchase #2	$116.38	13.623%	$132.2344	$132.23	$132.25	$132.20
Purchase #3	$95.77	7.370%	$102.8282	$102.83	$102.85	$102.80
Purchase #4	$137.44	13.782%	$156.382	$156.38	$156.40	$156.40
Purchase #5	$95.76	12.265%	$107.505	$107.51	$107.50	$107.50
Purchase #6	$227.99	6.854%	$243.6164	$243.62	$243.60	$243.60
Purchase #7	$88.56	13.708%	$100.6998	$100.70	$100.70	$100.70
7 purchase totals =	$831.71		$915.3851	$915.39	$915.40	$915.30