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	$208.66	10.417%	$230.3961	$230.40	$230.40	$230.40
Purchase #2	$63.81	5.778%	$67.4969	$67.50	$67.50	$67.50
Purchase #3	$25.66	11.536%	$28.6201	$28.62	$28.60	$28.60
Purchase #4	$125.89	13.659%	$143.0853	$143.09	$143.10	$143.10
Purchase #5	$238.38	10.698%	$263.8819	$263.88	$263.90	$263.90
Purchase #6	$124.35	5.345%	$130.9965	$131.00	$131.00	$131.00
Purchase #7	$144.88	9.718%	$158.9594	$158.96	$158.95	$159.00
7 purchase totals =	$931.63		$1,023.4362	$1,023.45	$1,023.45	$1,023.50