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	$152.53	5.520%	$160.9497	$160.95	$160.95	$160.90
Purchase #2	$17.50	12.410%	$19.6718	$19.67	$19.65	$19.70
Purchase #3	$197.37	8.770%	$214.6793	$214.68	$214.70	$214.70
Purchase #4	$67.93	6.857%	$72.588	$72.59	$72.60	$72.60
Purchase #5	$225.52	11.498%	$251.4503	$251.45	$251.45	$251.50
Purchase #6	$159.59	7.213%	$171.1012	$171.10	$171.10	$171.10
Purchase #7	$184.83	6.573%	$196.9789	$196.98	$197.00	$197.00
7 purchase totals =	$1,005.27		$1,087.4192	$1,087.42	$1,087.45	$1,087.50