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	$136.55	13.306%	$154.7193	$154.72	$154.70	$154.70
Purchase #2	$71.28	10.103%	$78.4814	$78.48	$78.50	$78.50
Purchase #3	$185.91	5.407%	$195.9622	$195.96	$195.95	$196.00
Purchase #4	$10.39	4.257%	$10.8323	$10.83	$10.85	$10.80
Purchase #5	$96.31	3.641%	$99.8166	$99.82	$99.80	$99.80
Purchase #6	$183.89	3.639%	$190.5818	$190.58	$190.60	$190.60
Purchase #7	$153.51	8.461%	$166.4985	$166.50	$166.50	$166.50
7 purchase totals =	$837.84		$896.8921	$896.89	$896.90	$896.90