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	$33.27	7.542%	$35.7792	$35.78	$35.80	$35.80
Purchase #2	$174.57	7.226%	$187.1844	$187.18	$187.20	$187.20
Purchase #3	$42.29	8.733%	$45.9832	$45.98	$46.00	$46.00
Purchase #4	$34.57	7.496%	$37.1614	$37.16	$37.15	$37.20
Purchase #5	$59.80	10.137%	$65.8619	$65.86	$65.85	$65.90
Purchase #6	$41.31	3.708%	$42.8418	$42.84	$42.85	$42.80
Purchase #7	$192.26	6.857%	$205.4433	$205.44	$205.45	$205.40
7 purchase totals =	$578.07		$620.2552	$620.24	$620.30	$620.30