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	$27.45	4.439%	$28.6685	$28.67	$28.65	$28.70
Purchase #2	$56.74	9.195%	$61.9572	$61.96	$61.95	$62.00
Purchase #3	$93.83	7.376%	$100.7509	$100.75	$100.75	$100.80
Purchase #4	$80.36	10.159%	$88.5238	$88.52	$88.50	$88.50
Purchase #5	$192.51	8.784%	$209.4201	$209.42	$209.40	$209.40
Purchase #6	$155.90	5.710%	$164.8019	$164.80	$164.80	$164.80
Purchase #7	$124.92	13.126%	$141.317	$141.32	$141.30	$141.30
7 purchase totals =	$731.71		$795.4394	$795.44	$795.35	$795.50