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	$42.67	8.429%	$46.2667	$46.27	$46.25	$46.30
Purchase #2	$62.47	5.749%	$66.0614	$66.06	$66.05	$66.10
Purchase #3	$219.48	11.707%	$245.1745	$245.17	$245.15	$245.20
Purchase #4	$142.63	12.655%	$160.6798	$160.68	$160.70	$160.70
Purchase #5	$158.82	5.849%	$168.1094	$168.11	$168.10	$168.10
Purchase #6	$225.57	13.527%	$256.0829	$256.08	$256.10	$256.10
Purchase #7	$132.32	4.125%	$137.7782	$137.78	$137.80	$137.80
7 purchase totals =	$983.96		$1,080.1529	$1,080.15	$1,080.15	$1,080.30