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	$238.82	11.329%	$265.8759	$265.88	$265.90	$265.90
Purchase #2	$47.75	13.671%	$54.2779	$54.28	$54.30	$54.30
Purchase #3	$9.45	9.870%	$10.3827	$10.38	$10.40	$10.40
Purchase #4	$136.92	9.580%	$150.0369	$150.04	$150.05	$150.00
Purchase #5	$56.99	3.714%	$59.1066	$59.11	$59.10	$59.10
Purchase #6	$163.87	13.780%	$186.4513	$186.45	$186.45	$186.50
Purchase #7	$97.56	8.177%	$105.5375	$105.54	$105.55	$105.50
7 purchase totals =	$751.36		$831.6688	$831.68	$831.75	$831.70