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	$84.71	9.307%	$92.594	$92.59	$92.60	$92.60
Purchase #2	$46.48	8.773%	$50.5577	$50.56	$50.55	$50.60
Purchase #3	$85.61	3.239%	$88.3829	$88.38	$88.40	$88.40
Purchase #4	$164.46	10.339%	$181.4635	$181.46	$181.45	$181.50
Purchase #5	$145.38	5.113%	$152.8133	$152.81	$152.80	$152.80
Purchase #6	$219.45	3.670%	$227.5038	$227.50	$227.50	$227.50
Purchase #7	$23.38	6.355%	$24.8658	$24.87	$24.85	$24.90
7 purchase totals =	$769.47		$818.1810	$818.17	$818.15	$818.30