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	$67.60	12.223%	$75.8627	$75.86	$75.85	$75.90
Purchase #2	$241.60	3.715%	$250.5754	$250.58	$250.60	$250.60
Purchase #3	$207.67	4.322%	$216.6455	$216.65	$216.65	$216.60
Purchase #4	$180.75	13.480%	$205.1151	$205.12	$205.10	$205.10
Purchase #5	$100.30	10.766%	$111.0983	$111.10	$111.10	$111.10
Purchase #6	$161.80	10.563%	$178.8909	$178.89	$178.90	$178.90
Purchase #7	$127.98	3.453%	$132.3991	$132.40	$132.40	$132.40
7 purchase totals =	$1,087.70		$1,170.5870	$1,170.60	$1,170.60	$1,170.60