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	$234.70	9.126%	$256.1187	$256.12	$256.10	$256.10
Purchase #2	$82.62	7.456%	$88.7801	$88.78	$88.80	$88.80
Purchase #3	$71.72	10.102%	$78.9652	$78.97	$78.95	$79.00
Purchase #4	$144.69	4.163%	$150.7134	$150.71	$150.70	$150.70
Purchase #5	$216.93	13.679%	$246.6039	$246.60	$246.60	$246.60
Purchase #6	$167.85	3.475%	$173.6828	$173.68	$173.70	$173.70
Purchase #7	$9.90	6.449%	$10.5385	$10.54	$10.55	$10.50
7 purchase totals =	$928.41		$1,005.4026	$1,005.40	$1,005.40	$1,005.40