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	$50.48	13.417%	$57.2529	$57.25	$57.25	$57.30
Purchase #2	$97.89	13.532%	$111.1365	$111.14	$111.15	$111.10
Purchase #3	$216.89	10.835%	$240.39	$240.39	$240.40	$240.40
Purchase #4	$77.27	10.835%	$85.6422	$85.64	$85.65	$85.60
Purchase #5	$195.49	5.177%	$205.6105	$205.61	$205.60	$205.60
Purchase #6	$124.64	8.683%	$135.4625	$135.46	$135.45	$135.50
Purchase #7	$103.96	8.491%	$112.7872	$112.79	$112.80	$112.80
7 purchase totals =	$866.62		$948.2818	$948.28	$948.30	$948.30