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	$108.35	7.575%	$116.5575	$116.56	$116.55	$116.60
Purchase #2	$79.54	11.549%	$88.7261	$88.73	$88.75	$88.70
Purchase #3	$163.73	10.478%	$180.8856	$180.89	$180.90	$180.90
Purchase #4	$207.52	12.595%	$233.6571	$233.66	$233.65	$233.70
Purchase #5	$69.26	4.540%	$72.4044	$72.40	$72.40	$72.40
Purchase #6	$127.47	12.577%	$143.5019	$143.50	$143.50	$143.50
Purchase #7	$42.77	8.247%	$46.2972	$46.30	$46.30	$46.30
7 purchase totals =	$798.64		$882.0298	$882.04	$882.05	$882.10