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	$35.54	9.217%	$38.8157	$38.82	$38.80	$38.80
Purchase #2	$150.82	11.510%	$168.1794	$168.18	$168.20	$168.20
Purchase #3	$51.67	6.766%	$55.166	$55.17	$55.15	$55.20
Purchase #4	$70.79	11.609%	$79.008	$79.01	$79.00	$79.00
Purchase #5	$22.27	8.487%	$24.1601	$24.16	$24.15	$24.20
Purchase #6	$134.50	7.415%	$144.4732	$144.47	$144.45	$144.50
Purchase #7	$111.52	10.644%	$123.3902	$123.39	$123.40	$123.40
7 purchase totals =	$577.11		$633.1926	$633.20	$633.15	$633.30