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	$164.28	9.355%	$179.6484	$179.65	$179.65	$179.60
Purchase #2	$111.38	10.446%	$123.0148	$123.01	$123.00	$123.00
Purchase #3	$241.51	7.471%	$259.5532	$259.55	$259.55	$259.60
Purchase #4	$60.52	9.744%	$66.4171	$66.42	$66.40	$66.40
Purchase #5	$61.63	13.479%	$69.9371	$69.94	$69.95	$69.90
Purchase #6	$144.65	7.491%	$155.4857	$155.49	$155.50	$155.50
Purchase #7	$35.92	8.221%	$38.873	$38.87	$38.85	$38.90
7 purchase totals =	$819.89		$892.9293	$892.93	$892.90	$892.90