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	$240.76	9.717%	$264.1546	$264.15	$264.15	$264.20
Purchase #2	$31.49	9.871%	$34.5984	$34.60	$34.60	$34.60
Purchase #3	$116.35	6.464%	$123.8709	$123.87	$123.85	$123.90
Purchase #4	$131.95	8.702%	$143.4323	$143.43	$143.45	$143.40
Purchase #5	$57.82	11.130%	$64.2554	$64.26	$64.25	$64.30
Purchase #6	$12.27	9.638%	$13.4526	$13.45	$13.45	$13.50
Purchase #7	$150.92	11.541%	$168.3377	$168.34	$168.35	$168.30
7 purchase totals =	$741.56		$812.1019	$812.10	$812.10	$812.20