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	$150.59	13.395%	$170.7615	$170.76	$170.75	$170.80
Purchase #2	$68.64	13.756%	$78.0821	$78.08	$78.10	$78.10
Purchase #3	$247.55	4.464%	$258.6006	$258.60	$258.60	$258.60
Purchase #4	$23.73	7.347%	$25.4734	$25.47	$25.45	$25.50
Purchase #5	$162.70	8.259%	$176.1374	$176.14	$176.15	$176.10
Purchase #6	$209.77	11.795%	$234.5124	$234.51	$234.50	$234.50
Purchase #7	$193.51	3.778%	$200.8208	$200.82	$200.80	$200.80
7 purchase totals =	$1,056.49		$1,144.3882	$1,144.38	$1,144.35	$1,144.40