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	$226.33	5.280%	$238.2802	$238.28	$238.30	$238.30
Purchase #2	$173.25	4.462%	$180.9804	$180.98	$181.00	$181.00
Purchase #3	$50.61	7.157%	$54.2322	$54.23	$54.25	$54.20
Purchase #4	$106.39	5.666%	$112.4181	$112.42	$112.40	$112.40
Purchase #5	$91.95	9.766%	$100.9298	$100.93	$100.95	$100.90
Purchase #6	$51.49	10.429%	$56.8599	$56.86	$56.85	$56.90
Purchase #7	$222.81	7.545%	$239.621	$239.62	$239.60	$239.60
7 purchase totals =	$922.83		$983.3216	$983.32	$983.35	$983.30