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	$241.40	7.513%	$259.5364	$259.54	$259.55	$259.50
Purchase #2	$134.26	5.662%	$141.8618	$141.86	$141.85	$141.90
Purchase #3	$49.40	9.821%	$54.2516	$54.25	$54.25	$54.30
Purchase #4	$157.27	9.105%	$171.5894	$171.59	$171.60	$171.60
Purchase #5	$221.52	12.238%	$248.6296	$248.63	$248.65	$248.60
Purchase #6	$118.89	11.111%	$132.0999	$132.10	$132.10	$132.10
Purchase #7	$95.93	13.695%	$109.0676	$109.07	$109.05	$109.10
7 purchase totals =	$1,018.67		$1,117.0363	$1,117.04	$1,117.05	$1,117.10