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	$48.43	10.466%	$53.4987	$53.50	$53.50	$53.50
Purchase #2	$248.37	3.553%	$257.1946	$257.19	$257.20	$257.20
Purchase #3	$229.37	3.252%	$236.8291	$236.83	$236.85	$236.80
Purchase #4	$88.93	13.525%	$100.9578	$100.96	$100.95	$101.00
Purchase #5	$151.60	13.821%	$172.5526	$172.55	$172.55	$172.60
Purchase #6	$66.58	6.374%	$70.8238	$70.82	$70.80	$70.80
Purchase #7	$147.61	3.305%	$152.4885	$152.49	$152.50	$152.50
7 purchase totals =	$980.89		$1,044.3451	$1,044.34	$1,044.35	$1,044.40