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	$237.60	11.654%	$265.2899	$265.29	$265.30	$265.30
Purchase #2	$211.89	6.512%	$225.6883	$225.69	$225.70	$225.70
Purchase #3	$183.89	4.142%	$191.5067	$191.51	$191.50	$191.50
Purchase #4	$178.25	11.338%	$198.46	$198.46	$198.45	$198.50
Purchase #5	$197.29	3.811%	$204.8087	$204.81	$204.80	$204.80
Purchase #6	$88.71	12.857%	$100.1154	$100.12	$100.10	$100.10
Purchase #7	$29.41	9.182%	$32.1104	$32.11	$32.10	$32.10
7 purchase totals =	$1,127.04		$1,217.9794	$1,217.99	$1,217.95	$1,218.00