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	$205.71	12.340%	$231.0946	$231.09	$231.10	$231.10
Purchase #2	$103.60	5.373%	$109.1664	$109.17	$109.15	$109.20
Purchase #3	$24.55	3.665%	$25.4498	$25.45	$25.45	$25.40
Purchase #4	$242.27	13.358%	$274.6324	$274.63	$274.65	$274.60
Purchase #5	$192.70	9.344%	$210.7059	$210.71	$210.70	$210.70
Purchase #6	$109.80	6.151%	$116.5538	$116.55	$116.55	$116.60
Purchase #7	$74.32	11.654%	$82.9813	$82.98	$83.00	$83.00
7 purchase totals =	$952.95		$1,050.5842	$1,050.58	$1,050.60	$1,050.60