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	$60.61	5.676%	$64.0502	$64.05	$64.05	$64.10
Purchase #2	$137.52	4.342%	$143.4911	$143.49	$143.50	$143.50
Purchase #3	$208.52	11.734%	$232.9877	$232.99	$233.00	$233.00
Purchase #4	$43.54	11.528%	$48.5593	$48.56	$48.55	$48.60
Purchase #5	$10.25	12.252%	$11.5058	$11.51	$11.50	$11.50
Purchase #6	$20.74	5.286%	$21.8363	$21.84	$21.85	$21.80
Purchase #7	$95.43	5.681%	$100.8514	$100.85	$100.85	$100.90
7 purchase totals =	$576.61		$623.2818	$623.29	$623.30	$623.40