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	$34.38	4.349%	$35.8752	$35.88	$35.90	$35.90
Purchase #2	$104.35	4.856%	$109.4172	$109.42	$109.40	$109.40
Purchase #3	$10.43	8.389%	$11.305	$11.31	$11.30	$11.30
Purchase #4	$158.42	13.659%	$180.0586	$180.06	$180.05	$180.10
Purchase #5	$82.75	11.153%	$91.9791	$91.98	$92.00	$92.00
Purchase #6	$45.47	12.254%	$51.0419	$51.04	$51.05	$51.00
Purchase #7	$56.25	11.748%	$62.8583	$62.86	$62.85	$62.90
7 purchase totals =	$492.05		$542.5353	$542.55	$542.55	$542.60