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	$41.45	4.461%	$43.2991	$43.30	$43.30	$43.30
Purchase #2	$68.36	7.268%	$73.3284	$73.33	$73.35	$73.30
Purchase #3	$113.93	3.824%	$118.2867	$118.29	$118.30	$118.30
Purchase #4	$142.99	3.576%	$148.1033	$148.10	$148.10	$148.10
Purchase #5	$34.98	8.521%	$37.9606	$37.96	$37.95	$38.00
Purchase #6	$225.25	13.480%	$255.6137	$255.61	$255.60	$255.60
Purchase #7	$128.30	11.827%	$143.474	$143.47	$143.45	$143.50
7 purchase totals =	$755.26		$820.0658	$820.06	$820.05	$820.10