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	$192.82	8.177%	$208.5869	$208.59	$208.60	$208.60
Purchase #2	$148.31	11.634%	$165.5644	$165.56	$165.55	$165.60
Purchase #3	$161.54	6.532%	$172.0918	$172.09	$172.10	$172.10
Purchase #4	$90.32	13.156%	$102.2025	$102.20	$102.20	$102.20
Purchase #5	$31.66	4.329%	$33.0306	$33.03	$33.05	$33.00
Purchase #6	$201.82	12.680%	$227.4108	$227.41	$227.40	$227.40
Purchase #7	$176.49	7.711%	$190.0991	$190.10	$190.10	$190.10
7 purchase totals =	$1,002.96		$1,098.9861	$1,098.98	$1,099.00	$1,099.00