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	$205.48	11.214%	$228.5225	$228.52	$228.50	$228.50
Purchase #2	$241.90	10.848%	$268.1413	$268.14	$268.15	$268.10
Purchase #3	$75.72	3.758%	$78.5656	$78.57	$78.55	$78.60
Purchase #4	$239.90	9.839%	$263.5038	$263.50	$263.50	$263.50
Purchase #5	$106.87	5.263%	$112.4946	$112.49	$112.50	$112.50
Purchase #6	$106.39	9.522%	$116.5205	$116.52	$116.50	$116.50
Purchase #7	$194.96	12.705%	$219.7297	$219.73	$219.75	$219.70
7 purchase totals =	$1,171.22		$1,287.4780	$1,287.47	$1,287.45	$1,287.40