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	$82.29	10.494%	$90.9255	$90.93	$90.95	$90.90
Purchase #2	$228.41	4.683%	$239.1064	$239.11	$239.10	$239.10
Purchase #3	$248.46	12.654%	$279.9001	$279.90	$279.90	$279.90
Purchase #4	$124.61	6.650%	$132.8966	$132.90	$132.90	$132.90
Purchase #5	$72.37	11.141%	$80.4327	$80.43	$80.45	$80.40
Purchase #6	$93.87	8.762%	$102.0949	$102.09	$102.10	$102.10
Purchase #7	$122.25	7.448%	$131.3552	$131.36	$131.35	$131.40
7 purchase totals =	$972.26		$1,056.7114	$1,056.72	$1,056.75	$1,056.70