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	$117.44	13.496%	$133.2897	$133.29	$133.30	$133.30
Purchase #2	$52.41	4.872%	$54.9634	$54.96	$54.95	$55.00
Purchase #3	$123.83	8.841%	$134.7778	$134.78	$134.80	$134.80
Purchase #4	$178.79	9.721%	$196.1702	$196.17	$196.15	$196.20
Purchase #5	$249.45	6.406%	$265.4298	$265.43	$265.45	$265.40
Purchase #6	$178.48	11.546%	$199.0873	$199.09	$199.10	$199.10
Purchase #7	$32.87	3.645%	$34.0681	$34.07	$34.05	$34.10
7 purchase totals =	$933.27		$1,017.7863	$1,017.79	$1,017.80	$1,017.90