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	$48.98	4.810%	$51.3359	$51.34	$51.35	$51.30
Purchase #2	$150.84	7.747%	$162.5256	$162.53	$162.55	$162.50
Purchase #3	$10.52	12.747%	$11.861	$11.86	$11.85	$11.90
Purchase #4	$246.51	10.572%	$272.571	$272.57	$272.55	$272.60
Purchase #5	$176.57	5.792%	$186.7969	$186.80	$186.80	$186.80
Purchase #6	$150.32	8.193%	$162.6357	$162.64	$162.65	$162.60
Purchase #7	$164.84	4.261%	$171.8638	$171.86	$171.85	$171.90
7 purchase totals =	$948.58		$1,019.5899	$1,019.60	$1,019.60	$1,019.60