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	$181.69	13.106%	$205.5023	$205.50	$205.50	$205.50
Purchase #2	$235.90	10.537%	$260.7568	$260.76	$260.75	$260.80
Purchase #3	$201.99	12.544%	$227.3276	$227.33	$227.35	$227.30
Purchase #4	$67.42	13.125%	$76.2689	$76.27	$76.25	$76.30
Purchase #5	$74.89	4.806%	$78.4892	$78.49	$78.50	$78.50
Purchase #6	$31.47	13.107%	$35.5948	$35.59	$35.60	$35.60
Purchase #7	$115.59	12.714%	$130.2861	$130.29	$130.30	$130.30
7 purchase totals =	$908.95		$1,014.2257	$1,014.23	$1,014.25	$1,014.30