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	$58.32	3.603%	$60.4213	$60.42	$60.40	$60.40
Purchase #2	$81.95	9.384%	$89.6402	$89.64	$89.65	$89.60
Purchase #3	$100.37	11.587%	$111.9999	$112.00	$112.00	$112.00
Purchase #4	$58.51	5.508%	$61.7327	$61.73	$61.75	$61.70
Purchase #5	$206.25	5.425%	$217.4391	$217.44	$217.45	$217.40
Purchase #6	$151.27	4.469%	$158.0303	$158.03	$158.05	$158.00
Purchase #7	$13.93	4.227%	$14.5188	$14.52	$14.50	$14.50
7 purchase totals =	$670.60		$713.7823	$713.78	$713.80	$713.60