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	$95.26	8.748%	$103.5933	$103.59	$103.60	$103.60
Purchase #2	$173.90	5.569%	$183.5845	$183.58	$183.60	$183.60
Purchase #3	$51.87	11.169%	$57.6634	$57.66	$57.65	$57.70
Purchase #4	$42.95	8.591%	$46.6398	$46.64	$46.65	$46.60
Purchase #5	$149.54	7.390%	$160.591	$160.59	$160.60	$160.60
Purchase #6	$207.60	13.603%	$235.8398	$235.84	$235.85	$235.80
Purchase #7	$195.46	13.850%	$222.5312	$222.53	$222.55	$222.50
7 purchase totals =	$916.58		$1,010.4430	$1,010.43	$1,010.50	$1,010.40