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	$194.65	11.646%	$217.3189	$217.32	$217.30	$217.30
Purchase #2	$177.40	10.831%	$196.6142	$196.61	$196.60	$196.60
Purchase #3	$249.84	13.387%	$283.2861	$283.29	$283.30	$283.30
Purchase #4	$72.78	9.553%	$79.7327	$79.73	$79.75	$79.70
Purchase #5	$33.61	8.405%	$36.4349	$36.43	$36.45	$36.40
Purchase #6	$101.78	3.817%	$105.6649	$105.66	$105.65	$105.70
Purchase #7	$18.34	6.296%	$19.4947	$19.49	$19.50	$19.50
7 purchase totals =	$848.40		$938.5464	$938.53	$938.55	$938.50