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	$178.53	4.756%	$187.0209	$187.02	$187.00	$187.00
Purchase #2	$55.30	13.248%	$62.6261	$62.63	$62.65	$62.60
Purchase #3	$227.60	12.757%	$256.6349	$256.63	$256.65	$256.60
Purchase #4	$105.27	13.544%	$119.5278	$119.53	$119.55	$119.50
Purchase #5	$145.27	3.784%	$150.767	$150.77	$150.75	$150.80
Purchase #6	$153.47	11.434%	$171.0178	$171.02	$171.00	$171.00
Purchase #7	$117.53	13.201%	$133.0451	$133.05	$133.05	$133.00
7 purchase totals =	$982.97		$1,080.6396	$1,080.65	$1,080.65	$1,080.50