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	$205.73	4.774%	$215.5516	$215.55	$215.55	$215.60
Purchase #2	$151.68	13.873%	$172.7226	$172.72	$172.70	$172.70
Purchase #3	$121.94	3.667%	$126.4115	$126.41	$126.40	$126.40
Purchase #4	$145.73	3.464%	$150.7781	$150.78	$150.80	$150.80
Purchase #5	$24.98	13.872%	$28.4452	$28.45	$28.45	$28.40
Purchase #6	$129.77	10.401%	$143.2674	$143.27	$143.25	$143.30
Purchase #7	$249.30	8.636%	$270.8295	$270.83	$270.85	$270.80
7 purchase totals =	$1,029.13		$1,108.0059	$1,108.01	$1,108.00	$1,108.00