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	$127.56	12.382%	$143.3545	$143.35	$143.35	$143.40
Purchase #2	$88.78	13.217%	$100.5141	$100.51	$100.50	$100.50
Purchase #3	$57.51	6.843%	$61.4454	$61.45	$61.45	$61.40
Purchase #4	$50.58	7.515%	$54.3811	$54.38	$54.40	$54.40
Purchase #5	$171.28	10.711%	$189.6258	$189.63	$189.65	$189.60
Purchase #6	$199.52	4.532%	$208.5622	$208.56	$208.55	$208.60
Purchase #7	$137.89	11.310%	$153.4854	$153.49	$153.50	$153.50
7 purchase totals =	$833.12		$911.3685	$911.37	$911.40	$911.40