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	$198.38	12.156%	$222.4951	$222.50	$222.50	$222.50
Purchase #2	$189.74	10.275%	$209.2358	$209.24	$209.25	$209.20
Purchase #3	$59.78	9.837%	$65.6606	$65.66	$65.65	$65.70
Purchase #4	$22.45	4.671%	$23.4986	$23.50	$23.50	$23.50
Purchase #5	$11.37	10.702%	$12.5868	$12.59	$12.60	$12.60
Purchase #6	$47.41	12.447%	$53.3111	$53.31	$53.30	$53.30
Purchase #7	$38.79	11.473%	$43.2404	$43.24	$43.25	$43.20
7 purchase totals =	$567.92		$630.0284	$630.04	$630.05	$630.00