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	$97.50	3.256%	$100.6746	$100.67	$100.65	$100.70
Purchase #2	$193.91	7.283%	$208.0325	$208.03	$208.05	$208.00
Purchase #3	$181.61	12.254%	$203.8645	$203.86	$203.85	$203.90
Purchase #4	$120.70	9.206%	$131.8116	$131.81	$131.80	$131.80
Purchase #5	$25.73	6.764%	$27.4704	$27.47	$27.45	$27.50
Purchase #6	$48.27	13.793%	$54.9279	$54.93	$54.95	$54.90
Purchase #7	$145.87	8.583%	$158.39	$158.39	$158.40	$158.40
7 purchase totals =	$813.59		$885.1715	$885.16	$885.15	$885.20