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	$173.93	10.361%	$191.9509	$191.95	$191.95	$192.00
Purchase #2	$227.29	12.583%	$255.8899	$255.89	$255.90	$255.90
Purchase #3	$26.35	4.117%	$27.4348	$27.43	$27.45	$27.40
Purchase #4	$213.51	6.429%	$227.2366	$227.24	$227.25	$227.20
Purchase #5	$36.44	8.781%	$39.6398	$39.64	$39.65	$39.60
Purchase #6	$149.51	3.604%	$154.8983	$154.90	$154.90	$154.90
Purchase #7	$39.67	10.362%	$43.7806	$43.78	$43.80	$43.80
7 purchase totals =	$866.70		$940.8309	$940.83	$940.90	$940.80