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	$62.44	4.265%	$65.1031	$65.10	$65.10	$65.10
Purchase #2	$118.64	10.836%	$131.4958	$131.50	$131.50	$131.50
Purchase #3	$168.67	4.854%	$176.8572	$176.86	$176.85	$176.90
Purchase #4	$156.56	9.529%	$171.4786	$171.48	$171.50	$171.50
Purchase #5	$153.27	12.762%	$172.8303	$172.83	$172.85	$172.80
Purchase #6	$169.67	5.112%	$178.3435	$178.34	$178.35	$178.30
Purchase #7	$171.94	13.124%	$194.5054	$194.51	$194.50	$194.50
7 purchase totals =	$1,001.19		$1,090.6139	$1,090.62	$1,090.65	$1,090.60