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	$33.96	13.215%	$38.4478	$38.45	$38.45	$38.40
Purchase #2	$219.28	10.210%	$241.6685	$241.67	$241.65	$241.70
Purchase #3	$172.52	4.654%	$180.5491	$180.55	$180.55	$180.50
Purchase #4	$75.98	10.727%	$84.1304	$84.13	$84.15	$84.10
Purchase #5	$116.31	6.410%	$123.7655	$123.77	$123.75	$123.80
Purchase #6	$158.31	5.742%	$167.4002	$167.40	$167.40	$167.40
Purchase #7	$182.78	9.691%	$200.4932	$200.49	$200.50	$200.50
7 purchase totals =	$959.14		$1,036.4547	$1,036.46	$1,036.45	$1,036.40