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	$101.25	3.465%	$104.7583	$104.76	$104.75	$104.80
Purchase #2	$185.59	13.394%	$210.4479	$210.45	$210.45	$210.40
Purchase #3	$20.68	5.528%	$21.8232	$21.82	$21.80	$21.80
Purchase #4	$40.51	6.424%	$43.1124	$43.11	$43.10	$43.10
Purchase #5	$56.70	4.730%	$59.3819	$59.38	$59.40	$59.40
Purchase #6	$46.28	6.803%	$49.4284	$49.43	$49.45	$49.40
Purchase #7	$173.49	6.538%	$184.8328	$184.83	$184.85	$184.80
7 purchase totals =	$624.50		$673.7849	$673.78	$673.80	$673.70