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	$240.65	11.622%	$268.6183	$268.62	$268.60	$268.60
Purchase #2	$134.73	11.408%	$150.1	$150.10	$150.10	$150.10
Purchase #3	$114.66	10.242%	$126.4035	$126.40	$126.40	$126.40
Purchase #4	$30.42	6.545%	$32.411	$32.41	$32.40	$32.40
Purchase #5	$56.37	9.751%	$61.8666	$61.87	$61.85	$61.90
Purchase #6	$134.92	5.444%	$142.265	$142.27	$142.25	$142.30
Purchase #7	$240.42	5.585%	$253.8475	$253.85	$253.85	$253.80
7 purchase totals =	$952.17		$1,035.5119	$1,035.52	$1,035.45	$1,035.50