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	$174.82	10.131%	$192.531	$192.53	$192.55	$192.50
Purchase #2	$188.51	4.122%	$196.2804	$196.28	$196.30	$196.30
Purchase #3	$28.86	12.245%	$32.3939	$32.39	$32.40	$32.40
Purchase #4	$121.94	12.412%	$137.0752	$137.08	$137.10	$137.10
Purchase #5	$85.35	10.142%	$94.0062	$94.01	$94.00	$94.00
Purchase #6	$116.58	13.458%	$132.2693	$132.27	$132.25	$132.30
Purchase #7	$18.46	6.131%	$19.5918	$19.59	$19.60	$19.60
7 purchase totals =	$734.52		$804.1478	$804.15	$804.20	$804.20