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	$158.60	10.412%	$175.1134	$175.11	$175.10	$175.10
Purchase #2	$153.37	7.301%	$164.5675	$164.57	$164.55	$164.60
Purchase #3	$140.88	12.517%	$158.5139	$158.51	$158.50	$158.50
Purchase #4	$127.39	13.518%	$144.6106	$144.61	$144.60	$144.60
Purchase #5	$167.55	13.390%	$189.9849	$189.98	$190.00	$190.00
Purchase #6	$119.70	11.192%	$133.0968	$133.10	$133.10	$133.10
Purchase #7	$154.36	13.580%	$175.3221	$175.32	$175.30	$175.30
7 purchase totals =	$1,021.85		$1,141.2092	$1,141.20	$1,141.15	$1,141.20