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	$135.62	5.790%	$143.4724	$143.47	$143.45	$143.50
Purchase #2	$183.40	6.307%	$194.967	$194.97	$194.95	$195.00
Purchase #3	$112.80	13.439%	$127.9592	$127.96	$127.95	$128.00
Purchase #4	$156.91	4.848%	$164.517	$164.52	$164.50	$164.50
Purchase #5	$170.74	3.162%	$176.1388	$176.14	$176.15	$176.10
Purchase #6	$109.55	7.769%	$118.0609	$118.06	$118.05	$118.10
Purchase #7	$90.96	3.179%	$93.8516	$93.85	$93.85	$93.90
7 purchase totals =	$959.98		$1,018.9669	$1,018.97	$1,018.90	$1,019.10