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	$146.78	4.745%	$153.7447	$153.74	$153.75	$153.70
Purchase #2	$39.72	4.714%	$41.5924	$41.59	$41.60	$41.60
Purchase #3	$176.89	10.200%	$194.9328	$194.93	$194.95	$194.90
Purchase #4	$222.80	12.672%	$251.0332	$251.03	$251.05	$251.00
Purchase #5	$118.91	7.239%	$127.5179	$127.52	$127.50	$127.50
Purchase #6	$66.39	6.822%	$70.9191	$70.92	$70.90	$70.90
Purchase #7	$61.89	9.304%	$67.6482	$67.65	$67.65	$67.60
7 purchase totals =	$833.38		$907.3883	$907.38	$907.40	$907.20