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	$66.65	8.670%	$72.4286	$72.43	$72.45	$72.40
Purchase #2	$15.67	12.401%	$17.6132	$17.61	$17.60	$17.60
Purchase #3	$93.35	3.373%	$96.4987	$96.50	$96.50	$96.50
Purchase #4	$133.46	8.754%	$145.1431	$145.14	$145.15	$145.10
Purchase #5	$183.77	4.625%	$192.2694	$192.27	$192.25	$192.30
Purchase #6	$65.85	10.577%	$72.815	$72.82	$72.80	$72.80
Purchase #7	$127.98	10.556%	$141.4896	$141.49	$141.50	$141.50
7 purchase totals =	$686.73		$738.2576	$738.26	$738.25	$738.20