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	$111.88	10.667%	$123.8142	$123.81	$123.80	$123.80
Purchase #2	$85.77	4.522%	$89.6485	$89.65	$89.65	$89.60
Purchase #3	$5.47	6.427%	$5.8216	$5.82	$5.80	$5.80
Purchase #4	$50.81	3.441%	$52.5584	$52.56	$52.55	$52.60
Purchase #5	$225.55	5.383%	$237.6914	$237.69	$237.70	$237.70
Purchase #6	$103.84	13.680%	$118.0453	$118.05	$118.05	$118.00
Purchase #7	$230.40	11.526%	$256.9559	$256.96	$256.95	$257.00
7 purchase totals =	$813.72		$884.5353	$884.54	$884.50	$884.50