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	$29.27	4.517%	$30.5921	$30.59	$30.60	$30.60
Purchase #2	$112.65	13.194%	$127.513	$127.51	$127.50	$127.50
Purchase #3	$156.54	7.626%	$168.4777	$168.48	$168.50	$168.50
Purchase #4	$226.70	5.341%	$238.808	$238.81	$238.80	$238.80
Purchase #5	$204.27	11.226%	$227.2014	$227.20	$227.20	$227.20
Purchase #6	$118.89	10.118%	$130.9193	$130.92	$130.90	$130.90
Purchase #7	$177.66	10.652%	$196.5843	$196.58	$196.60	$196.60
7 purchase totals =	$1,025.98		$1,120.0958	$1,120.09	$1,120.10	$1,120.10