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	$68.70	4.862%	$72.0402	$72.04	$72.05	$72.00
Purchase #2	$208.27	13.111%	$235.5763	$235.58	$235.60	$235.60
Purchase #3	$7.68	12.309%	$8.6253	$8.63	$8.65	$8.60
Purchase #4	$19.55	4.695%	$20.4679	$20.47	$20.45	$20.50
Purchase #5	$93.85	5.795%	$99.2886	$99.29	$99.30	$99.30
Purchase #6	$124.39	13.672%	$141.3966	$141.40	$141.40	$141.40
Purchase #7	$68.64	5.322%	$72.293	$72.29	$72.30	$72.30
7 purchase totals =	$591.08		$649.6879	$649.70	$649.75	$649.70