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	$207.65	7.843%	$223.936	$223.94	$223.95	$223.90
Purchase #2	$49.83	10.353%	$54.9889	$54.99	$55.00	$55.00
Purchase #3	$137.68	5.793%	$145.6558	$145.66	$145.65	$145.70
Purchase #4	$43.60	3.795%	$45.2546	$45.25	$45.25	$45.30
Purchase #5	$151.45	8.647%	$164.5459	$164.55	$164.55	$164.50
Purchase #6	$24.42	11.604%	$27.2537	$27.25	$27.25	$27.30
Purchase #7	$95.64	9.231%	$104.4685	$104.47	$104.45	$104.50
7 purchase totals =	$710.27		$766.1034	$766.11	$766.10	$766.20