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	$212.61	9.575%	$232.9674	$232.97	$232.95	$233.00
Purchase #2	$173.61	13.370%	$196.8217	$196.82	$196.80	$196.80
Purchase #3	$160.64	7.225%	$172.2462	$172.25	$172.25	$172.20
Purchase #4	$65.65	9.689%	$72.0108	$72.01	$72.00	$72.00
Purchase #5	$240.28	10.805%	$266.2423	$266.24	$266.25	$266.20
Purchase #6	$134.67	13.383%	$152.6929	$152.69	$152.70	$152.70
Purchase #7	$51.30	8.392%	$55.6051	$55.61	$55.60	$55.60
7 purchase totals =	$1,038.76		$1,148.5864	$1,148.59	$1,148.55	$1,148.50