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	$146.59	3.667%	$151.9655	$151.97	$151.95	$152.00
Purchase #2	$171.48	3.420%	$177.3446	$177.34	$177.35	$177.30
Purchase #3	$192.91	9.509%	$211.2538	$211.25	$211.25	$211.30
Purchase #4	$26.70	10.380%	$29.4715	$29.47	$29.45	$29.50
Purchase #5	$165.29	4.430%	$172.6123	$172.61	$172.60	$172.60
Purchase #6	$68.77	13.622%	$78.1378	$78.14	$78.15	$78.10
Purchase #7	$87.34	12.295%	$98.0785	$98.08	$98.10	$98.10
7 purchase totals =	$859.08		$918.8640	$918.86	$918.85	$918.90