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	$161.83	5.317%	$170.4345	$170.43	$170.45	$170.40
Purchase #2	$28.62	4.461%	$29.8967	$29.90	$29.90	$29.90
Purchase #3	$95.78	4.852%	$100.4272	$100.43	$100.45	$100.40
Purchase #4	$231.67	7.213%	$248.3804	$248.38	$248.40	$248.40
Purchase #5	$64.92	11.174%	$72.1742	$72.17	$72.15	$72.20
Purchase #6	$24.50	4.127%	$25.5111	$25.51	$25.50	$25.50
Purchase #7	$66.54	8.849%	$72.4281	$72.43	$72.45	$72.40
7 purchase totals =	$673.86		$719.2522	$719.25	$719.30	$719.20