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	$203.28	12.548%	$228.7876	$228.79	$228.80	$228.80
Purchase #2	$93.76	10.765%	$103.8533	$103.85	$103.85	$103.90
Purchase #3	$19.50	6.683%	$20.8032	$20.80	$20.80	$20.80
Purchase #4	$161.67	7.509%	$173.8098	$173.81	$173.80	$173.80
Purchase #5	$200.91	12.266%	$225.5536	$225.55	$225.55	$225.60
Purchase #6	$240.63	5.491%	$253.843	$253.84	$253.85	$253.80
Purchase #7	$173.78	9.503%	$190.2943	$190.29	$190.30	$190.30
7 purchase totals =	$1,093.53		$1,196.9448	$1,196.93	$1,196.95	$1,197.00