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	$181.72	5.615%	$191.9236	$191.92	$191.90	$191.90
Purchase #2	$215.32	12.786%	$242.8508	$242.85	$242.85	$242.90
Purchase #3	$158.33	3.800%	$164.3465	$164.35	$164.35	$164.30
Purchase #4	$116.83	8.234%	$126.4498	$126.45	$126.45	$126.40
Purchase #5	$58.73	13.268%	$66.5223	$66.52	$66.50	$66.50
Purchase #6	$181.35	6.262%	$192.7061	$192.71	$192.70	$192.70
Purchase #7	$51.88	12.127%	$58.1715	$58.17	$58.15	$58.20
7 purchase totals =	$964.16		$1,042.9706	$1,042.97	$1,042.90	$1,042.90