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	$118.54	11.852%	$132.5894	$132.59	$132.60	$132.60
Purchase #2	$101.25	9.790%	$111.1624	$111.16	$111.15	$111.20
Purchase #3	$179.42	6.271%	$190.6714	$190.67	$190.65	$190.70
Purchase #4	$154.33	6.168%	$163.8491	$163.85	$163.85	$163.80
Purchase #5	$171.37	9.873%	$188.2894	$188.29	$188.30	$188.30
Purchase #6	$112.39	13.385%	$127.4334	$127.43	$127.45	$127.40
Purchase #7	$162.28	12.774%	$183.0096	$183.01	$183.00	$183.00
7 purchase totals =	$999.58		$1,097.0047	$1,097.00	$1,097.00	$1,097.00