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	$87.60	13.463%	$99.3936	$99.39	$99.40	$99.40
Purchase #2	$104.46	11.437%	$116.4071	$116.41	$116.40	$116.40
Purchase #3	$77.48	5.120%	$81.447	$81.45	$81.45	$81.40
Purchase #4	$94.74	11.325%	$105.4693	$105.47	$105.45	$105.50
Purchase #5	$80.34	7.532%	$86.3912	$86.39	$86.40	$86.40
Purchase #6	$190.54	10.724%	$210.9735	$210.97	$210.95	$211.00
Purchase #7	$9.61	6.411%	$10.2261	$10.23	$10.25	$10.20
7 purchase totals =	$644.77		$710.3078	$710.31	$710.30	$710.30