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	$100.76	4.628%	$105.4232	$105.42	$105.40	$105.40
Purchase #2	$137.95	11.307%	$153.548	$153.55	$153.55	$153.50
Purchase #3	$154.58	7.862%	$166.7331	$166.73	$166.75	$166.70
Purchase #4	$224.76	13.870%	$255.9342	$255.93	$255.95	$255.90
Purchase #5	$106.81	10.384%	$117.9012	$117.90	$117.90	$117.90
Purchase #6	$191.58	13.284%	$217.0295	$217.03	$217.05	$217.00
Purchase #7	$240.61	7.742%	$259.238	$259.24	$259.25	$259.20
7 purchase totals =	$1,157.05		$1,275.8072	$1,275.80	$1,275.85	$1,275.60