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	$249.98	9.248%	$273.0982	$273.10	$273.10	$273.10
Purchase #2	$104.60	6.627%	$111.5318	$111.53	$111.55	$111.50
Purchase #3	$216.48	11.537%	$241.4553	$241.46	$241.45	$241.50
Purchase #4	$128.69	6.815%	$137.4602	$137.46	$137.45	$137.50
Purchase #5	$21.76	5.541%	$22.9657	$22.97	$22.95	$23.00
Purchase #6	$146.69	4.358%	$153.0828	$153.08	$153.10	$153.10
Purchase #7	$178.83	7.845%	$192.8592	$192.86	$192.85	$192.90
7 purchase totals =	$1,047.03		$1,132.4532	$1,132.46	$1,132.45	$1,132.60