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	$171.86	8.189%	$185.9336	$185.93	$185.95	$185.90
Purchase #2	$129.79	3.119%	$133.8382	$133.84	$133.85	$133.80
Purchase #3	$18.61	13.445%	$21.1121	$21.11	$21.10	$21.10
Purchase #4	$63.87	12.847%	$72.0754	$72.08	$72.10	$72.10
Purchase #5	$151.47	9.548%	$165.9324	$165.93	$165.95	$165.90
Purchase #6	$77.51	6.674%	$82.683	$82.68	$82.70	$82.70
Purchase #7	$241.91	4.867%	$253.6838	$253.68	$253.70	$253.70
7 purchase totals =	$855.02		$915.2585	$915.25	$915.35	$915.20