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	$35.93	7.681%	$38.6898	$38.69	$38.70	$38.70
Purchase #2	$45.77	8.362%	$49.5973	$49.60	$49.60	$49.60
Purchase #3	$119.37	3.112%	$123.0848	$123.08	$123.10	$123.10
Purchase #4	$54.47	11.277%	$60.6126	$60.61	$60.60	$60.60
Purchase #5	$204.73	3.389%	$211.6683	$211.67	$211.65	$211.70
Purchase #6	$133.54	11.174%	$148.4618	$148.46	$148.45	$148.50
Purchase #7	$6.87	10.262%	$7.575	$7.58	$7.60	$7.60
7 purchase totals =	$600.68		$639.6896	$639.69	$639.70	$639.80