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	$52.54	5.505%	$55.4323	$55.43	$55.45	$55.40
Purchase #2	$51.29	4.154%	$53.4206	$53.42	$53.40	$53.40
Purchase #3	$117.84	8.156%	$127.451	$127.45	$127.45	$127.50
Purchase #4	$238.51	5.645%	$251.9739	$251.97	$251.95	$252.00
Purchase #5	$26.50	12.527%	$29.8197	$29.82	$29.80	$29.80
Purchase #6	$154.58	10.838%	$171.3334	$171.33	$171.35	$171.30
Purchase #7	$112.54	10.120%	$123.929	$123.93	$123.95	$123.90
7 purchase totals =	$753.80		$813.3599	$813.35	$813.35	$813.30