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	$32.69	9.461%	$35.7828	$35.78	$35.80	$35.80
Purchase #2	$238.45	11.321%	$265.4449	$265.44	$265.45	$265.40
Purchase #3	$103.67	13.434%	$117.597	$117.60	$117.60	$117.60
Purchase #4	$160.40	4.393%	$167.4464	$167.45	$167.45	$167.40
Purchase #5	$219.32	3.188%	$226.3119	$226.31	$226.30	$226.30
Purchase #6	$50.80	13.536%	$57.6763	$57.68	$57.70	$57.70
Purchase #7	$247.92	3.871%	$257.517	$257.52	$257.50	$257.50
7 purchase totals =	$1,053.25		$1,127.7763	$1,127.78	$1,127.80	$1,127.70