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	$62.83	7.584%	$67.595	$67.60	$67.60	$67.60
Purchase #2	$63.33	8.328%	$68.6041	$68.60	$68.60	$68.60
Purchase #3	$26.68	6.143%	$28.319	$28.32	$28.30	$28.30
Purchase #4	$197.64	5.158%	$207.8343	$207.83	$207.85	$207.80
Purchase #5	$11.26	9.508%	$12.3306	$12.33	$12.35	$12.30
Purchase #6	$206.29	5.205%	$217.0274	$217.03	$217.05	$217.00
Purchase #7	$33.79	11.256%	$37.5934	$37.59	$37.60	$37.60
7 purchase totals =	$601.82		$639.3038	$639.30	$639.35	$639.20