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	$76.82	11.736%	$85.8356	$85.84	$85.85	$85.80
Purchase #2	$36.52	11.631%	$40.7676	$40.77	$40.75	$40.80
Purchase #3	$165.52	7.847%	$178.5084	$178.51	$178.50	$178.50
Purchase #4	$114.83	3.133%	$118.4276	$118.43	$118.45	$118.40
Purchase #5	$113.90	12.451%	$128.0817	$128.08	$128.10	$128.10
Purchase #6	$56.64	7.589%	$60.9384	$60.94	$60.95	$60.90
Purchase #7	$220.48	13.575%	$250.4102	$250.41	$250.40	$250.40
7 purchase totals =	$784.71		$862.9695	$862.98	$863.00	$862.90