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	$150.62	6.615%	$160.5835	$160.58	$160.60	$160.60
Purchase #2	$38.43	13.249%	$43.5216	$43.52	$43.50	$43.50
Purchase #3	$179.64	4.571%	$187.8513	$187.85	$187.85	$187.90
Purchase #4	$93.91	12.105%	$105.2778	$105.28	$105.30	$105.30
Purchase #5	$235.56	9.478%	$257.8864	$257.89	$257.90	$257.90
Purchase #6	$210.80	12.467%	$237.0804	$237.08	$237.10	$237.10
Purchase #7	$138.61	12.155%	$155.458	$155.46	$155.45	$155.50
7 purchase totals =	$1,047.57		$1,147.6590	$1,147.66	$1,147.70	$1,147.80