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	$206.46	7.649%	$222.2521	$222.25	$222.25	$222.30
Purchase #2	$31.80	5.232%	$33.4638	$33.46	$33.45	$33.50
Purchase #3	$81.30	12.636%	$91.5731	$91.57	$91.55	$91.60
Purchase #4	$107.63	3.682%	$111.5929	$111.59	$111.60	$111.60
Purchase #5	$56.26	9.571%	$61.6446	$61.64	$61.65	$61.60
Purchase #6	$146.46	13.854%	$166.7506	$166.75	$166.75	$166.80
Purchase #7	$124.62	10.658%	$137.902	$137.90	$137.90	$137.90
7 purchase totals =	$754.53		$825.1791	$825.16	$825.15	$825.30