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	$59.98	9.285%	$65.5491	$65.55	$65.55	$65.50
Purchase #2	$222.77	8.394%	$241.4693	$241.47	$241.45	$241.50
Purchase #3	$100.90	11.191%	$112.1917	$112.19	$112.20	$112.20
Purchase #4	$86.99	4.495%	$90.9002	$90.90	$90.90	$90.90
Purchase #5	$226.85	9.798%	$249.0768	$249.08	$249.10	$249.10
Purchase #6	$91.31	10.475%	$100.8747	$100.87	$100.85	$100.90
Purchase #7	$149.92	10.427%	$165.5522	$165.55	$165.55	$165.60
7 purchase totals =	$938.72		$1,025.6140	$1,025.61	$1,025.60	$1,025.70