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	$226.54	12.758%	$255.442	$255.44	$255.45	$255.40
Purchase #2	$78.71	13.205%	$89.1037	$89.10	$89.10	$89.10
Purchase #3	$222.93	7.612%	$239.8994	$239.90	$239.90	$239.90
Purchase #4	$14.53	4.573%	$15.1945	$15.19	$15.20	$15.20
Purchase #5	$16.79	3.636%	$17.4005	$17.40	$17.40	$17.40
Purchase #6	$230.81	3.301%	$238.429	$238.43	$238.45	$238.40
Purchase #7	$224.26	7.265%	$240.5525	$240.55	$240.55	$240.60
7 purchase totals =	$1,014.57		$1,096.0216	$1,096.01	$1,096.05	$1,096.00