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	$181.47	8.307%	$196.5447	$196.54	$196.55	$196.50
Purchase #2	$250.30	8.857%	$272.4691	$272.47	$272.45	$272.50
Purchase #3	$172.95	7.339%	$185.6428	$185.64	$185.65	$185.60
Purchase #4	$186.81	7.356%	$200.5517	$200.55	$200.55	$200.60
Purchase #5	$228.45	13.501%	$259.293	$259.29	$259.30	$259.30
Purchase #6	$221.38	9.268%	$241.8975	$241.90	$241.90	$241.90
Purchase #7	$142.27	10.855%	$157.7134	$157.71	$157.70	$157.70
7 purchase totals =	$1,383.63		$1,514.1122	$1,514.10	$1,514.10	$1,514.10