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	$137.58	10.187%	$151.5953	$151.60	$151.60	$151.60
Purchase #2	$132.33	5.338%	$139.3938	$139.39	$139.40	$139.40
Purchase #3	$182.40	4.315%	$190.2706	$190.27	$190.25	$190.30
Purchase #4	$156.82	9.738%	$172.0911	$172.09	$172.10	$172.10
Purchase #5	$28.69	11.475%	$31.9822	$31.98	$32.00	$32.00
Purchase #6	$20.34	6.614%	$21.6853	$21.69	$21.70	$21.70
Purchase #7	$103.60	3.271%	$106.9888	$106.99	$107.00	$107.00
7 purchase totals =	$761.76		$814.0071	$814.01	$814.05	$814.10