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	$218.84	9.419%	$239.4525	$239.45	$239.45	$239.50
Purchase #2	$228.71	5.544%	$241.3897	$241.39	$241.40	$241.40
Purchase #3	$213.82	13.258%	$242.1683	$242.17	$242.15	$242.20
Purchase #4	$88.78	4.286%	$92.5851	$92.59	$92.60	$92.60
Purchase #5	$169.30	6.231%	$179.8491	$179.85	$179.85	$179.80
Purchase #6	$95.85	4.415%	$100.0818	$100.08	$100.10	$100.10
Purchase #7	$156.77	6.572%	$167.0729	$167.07	$167.05	$167.10
7 purchase totals =	$1,172.07		$1,262.5994	$1,262.60	$1,262.60	$1,262.70