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	$228.71	4.361%	$238.684	$238.68	$238.70	$238.70
Purchase #2	$239.44	10.458%	$264.4806	$264.48	$264.50	$264.50
Purchase #3	$186.48	12.716%	$210.1928	$210.19	$210.20	$210.20
Purchase #4	$54.43	3.771%	$56.4826	$56.48	$56.50	$56.50
Purchase #5	$58.81	12.384%	$66.093	$66.09	$66.10	$66.10
Purchase #6	$10.27	5.675%	$10.8528	$10.85	$10.85	$10.90
Purchase #7	$142.29	12.737%	$160.4135	$160.41	$160.40	$160.40
7 purchase totals =	$920.43		$1,007.1993	$1,007.18	$1,007.25	$1,007.30