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	$156.79	10.245%	$172.8531	$172.85	$172.85	$172.90
Purchase #2	$224.55	7.745%	$241.9414	$241.94	$241.95	$241.90
Purchase #3	$75.82	9.435%	$82.9736	$82.97	$82.95	$83.00
Purchase #4	$172.60	5.848%	$182.6936	$182.69	$182.70	$182.70
Purchase #5	$120.92	9.680%	$132.6251	$132.63	$132.65	$132.60
Purchase #6	$181.34	5.214%	$190.7951	$190.80	$190.80	$190.80
Purchase #7	$63.31	6.793%	$67.6106	$67.61	$67.60	$67.60
7 purchase totals =	$995.33		$1,071.4925	$1,071.49	$1,071.50	$1,071.50