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	$52.37	5.843%	$55.43	$55.43	$55.45	$55.40
Purchase #2	$211.86	13.125%	$239.6666	$239.67	$239.65	$239.70
Purchase #3	$181.43	8.509%	$196.8679	$196.87	$196.85	$196.90
Purchase #4	$123.98	7.347%	$133.0888	$133.09	$133.10	$133.10
Purchase #5	$78.68	6.679%	$83.935	$83.94	$83.95	$83.90
Purchase #6	$191.39	6.214%	$203.283	$203.28	$203.30	$203.30
Purchase #7	$120.32	11.820%	$134.5418	$134.54	$134.55	$134.50
7 purchase totals =	$960.03		$1,046.8131	$1,046.82	$1,046.85	$1,046.80