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	$226.52	3.156%	$233.669	$233.67	$233.65	$233.70
Purchase #2	$177.62	10.266%	$195.8545	$195.85	$195.85	$195.90
Purchase #3	$83.58	3.435%	$86.451	$86.45	$86.45	$86.50
Purchase #4	$29.72	10.555%	$32.8569	$32.86	$32.85	$32.90
Purchase #5	$97.61	6.266%	$103.7262	$103.73	$103.75	$103.70
Purchase #6	$137.46	6.655%	$146.608	$146.61	$146.60	$146.60
Purchase #7	$158.28	11.478%	$176.4474	$176.45	$176.45	$176.40
7 purchase totals =	$910.79		$975.6130	$975.62	$975.60	$975.70