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	$116.41	5.825%	$123.1909	$123.19	$123.20	$123.20
Purchase #2	$55.31	10.694%	$61.2249	$61.22	$61.20	$61.20
Purchase #3	$199.57	12.718%	$224.9513	$224.95	$224.95	$225.00
Purchase #4	$249.61	5.136%	$262.43	$262.43	$262.45	$262.40
Purchase #5	$249.77	4.108%	$260.0306	$260.03	$260.05	$260.00
Purchase #6	$95.78	10.293%	$105.6386	$105.64	$105.65	$105.60
Purchase #7	$153.87	9.237%	$168.083	$168.08	$168.10	$168.10
7 purchase totals =	$1,120.32		$1,205.5493	$1,205.54	$1,205.60	$1,205.50