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	$64.92	5.521%	$68.5042	$68.50	$68.50	$68.50
Purchase #2	$112.59	4.719%	$117.9031	$117.90	$117.90	$117.90
Purchase #3	$245.35	7.389%	$263.4789	$263.48	$263.50	$263.50
Purchase #4	$134.38	3.739%	$139.4045	$139.40	$139.40	$139.40
Purchase #5	$92.60	8.306%	$100.2914	$100.29	$100.30	$100.30
Purchase #6	$134.32	13.601%	$152.5889	$152.59	$152.60	$152.60
Purchase #7	$11.45	7.421%	$12.2997	$12.30	$12.30	$12.30
7 purchase totals =	$795.61		$854.4707	$854.46	$854.50	$854.50