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	$69.84	6.181%	$74.1568	$74.16	$74.15	$74.20
Purchase #2	$116.28	9.204%	$126.9824	$126.98	$127.00	$127.00
Purchase #3	$79.85	7.564%	$85.8899	$85.89	$85.90	$85.90
Purchase #4	$148.70	9.331%	$162.5752	$162.58	$162.60	$162.60
Purchase #5	$96.42	7.306%	$103.4644	$103.46	$103.45	$103.50
Purchase #6	$48.79	11.665%	$54.4814	$54.48	$54.50	$54.50
Purchase #7	$155.99	7.520%	$167.7204	$167.72	$167.70	$167.70
7 purchase totals =	$715.87		$775.2705	$775.27	$775.30	$775.40