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	$153.77	5.518%	$162.255	$162.26	$162.25	$162.30
Purchase #2	$133.77	12.233%	$150.1341	$150.13	$150.15	$150.10
Purchase #3	$25.52	6.211%	$27.105	$27.11	$27.10	$27.10
Purchase #4	$9.38	7.727%	$10.1048	$10.10	$10.10	$10.10
Purchase #5	$44.50	3.184%	$45.9169	$45.92	$45.90	$45.90
Purchase #6	$18.88	12.640%	$21.2664	$21.27	$21.25	$21.30
Purchase #7	$146.41	5.589%	$154.5929	$154.59	$154.60	$154.60
7 purchase totals =	$532.23		$571.3751	$571.38	$571.35	$571.40