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	$129.41	10.642%	$143.1818	$143.18	$143.20	$143.20
Purchase #2	$12.28	13.416%	$13.9275	$13.93	$13.95	$13.90
Purchase #3	$244.77	8.391%	$265.3087	$265.31	$265.30	$265.30
Purchase #4	$138.73	3.553%	$143.6591	$143.66	$143.65	$143.70
Purchase #5	$233.30	10.749%	$258.3774	$258.38	$258.40	$258.40
Purchase #6	$42.46	13.488%	$48.187	$48.19	$48.20	$48.20
Purchase #7	$100.48	11.285%	$111.8192	$111.82	$111.80	$111.80
7 purchase totals =	$901.43		$984.4607	$984.47	$984.50	$984.50