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	$162.31	6.380%	$172.6654	$172.67	$172.65	$172.70
Purchase #2	$71.45	8.121%	$77.2525	$77.25	$77.25	$77.30
Purchase #3	$176.52	11.563%	$196.931	$196.93	$196.95	$196.90
Purchase #4	$134.43	12.765%	$151.59	$151.59	$151.60	$151.60
Purchase #5	$128.99	12.296%	$144.8506	$144.85	$144.85	$144.90
Purchase #6	$201.28	6.677%	$214.7195	$214.72	$214.70	$214.70
Purchase #7	$24.25	10.445%	$26.7829	$26.78	$26.80	$26.80
7 purchase totals =	$899.23		$984.7919	$984.79	$984.80	$984.90