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	$111.72	9.855%	$122.73	$122.73	$122.75	$122.70
Purchase #2	$119.96	6.462%	$127.7118	$127.71	$127.70	$127.70
Purchase #3	$110.87	11.226%	$123.3163	$123.32	$123.30	$123.30
Purchase #4	$215.67	7.327%	$231.4721	$231.47	$231.45	$231.50
Purchase #5	$208.46	4.602%	$218.0533	$218.05	$218.05	$218.10
Purchase #6	$91.92	9.848%	$100.9723	$100.97	$100.95	$101.00
Purchase #7	$150.38	3.696%	$155.938	$155.94	$155.95	$155.90
7 purchase totals =	$1,008.98		$1,080.1938	$1,080.19	$1,080.15	$1,080.20