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	$27.40	3.846%	$28.4538	$28.45	$28.45	$28.50
Purchase #2	$21.81	6.743%	$23.2806	$23.28	$23.30	$23.30
Purchase #3	$85.39	5.537%	$90.118	$90.12	$90.10	$90.10
Purchase #4	$47.54	8.726%	$51.6883	$51.69	$51.70	$51.70
Purchase #5	$56.36	4.757%	$59.041	$59.04	$59.05	$59.00
Purchase #6	$237.48	3.651%	$246.1504	$246.15	$246.15	$246.20
Purchase #7	$95.83	13.546%	$108.8111	$108.81	$108.80	$108.80
7 purchase totals =	$571.81		$607.5432	$607.54	$607.55	$607.60