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	$94.60	9.448%	$103.5378	$103.54	$103.55	$103.50
Purchase #2	$80.74	11.704%	$90.1898	$90.19	$90.20	$90.20
Purchase #3	$12.83	9.620%	$14.0642	$14.06	$14.05	$14.10
Purchase #4	$132.87	8.294%	$143.8902	$143.89	$143.90	$143.90
Purchase #5	$85.51	6.546%	$91.1075	$91.11	$91.10	$91.10
Purchase #6	$56.44	8.335%	$61.1443	$61.14	$61.15	$61.10
Purchase #7	$65.58	4.303%	$68.4019	$68.40	$68.40	$68.40
7 purchase totals =	$528.57		$572.3357	$572.33	$572.35	$572.30