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	$178.87	12.167%	$200.6331	$200.63	$200.65	$200.60
Purchase #2	$85.37	11.344%	$95.0544	$95.05	$95.05	$95.10
Purchase #3	$43.27	9.609%	$47.4278	$47.43	$47.45	$47.40
Purchase #4	$164.66	13.114%	$186.2535	$186.25	$186.25	$186.30
Purchase #5	$109.94	6.510%	$117.0971	$117.10	$117.10	$117.10
Purchase #6	$54.26	9.735%	$59.5422	$59.54	$59.55	$59.50
Purchase #7	$211.89	7.515%	$227.8135	$227.81	$227.80	$227.80
7 purchase totals =	$848.26		$933.8216	$933.81	$933.85	$933.80