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	$10.83	10.179%	$11.9324	$11.93	$11.95	$11.90
Purchase #2	$14.28	3.518%	$14.7824	$14.78	$14.80	$14.80
Purchase #3	$138.59	7.427%	$148.8831	$148.88	$148.90	$148.90
Purchase #4	$130.52	12.404%	$146.7097	$146.71	$146.70	$146.70
Purchase #5	$136.39	13.704%	$155.0809	$155.08	$155.10	$155.10
Purchase #6	$192.45	11.724%	$215.0128	$215.01	$215.00	$215.00
Purchase #7	$238.80	13.285%	$270.5246	$270.52	$270.50	$270.50
7 purchase totals =	$861.86		$962.9259	$962.91	$962.95	$962.90