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	$226.34	5.679%	$239.1938	$239.19	$239.20	$239.20
Purchase #2	$59.65	3.584%	$61.7879	$61.79	$61.80	$61.80
Purchase #3	$49.45	12.338%	$55.5511	$55.55	$55.55	$55.60
Purchase #4	$156.52	4.801%	$164.0345	$164.03	$164.05	$164.00
Purchase #5	$244.89	3.236%	$252.8146	$252.81	$252.80	$252.80
Purchase #6	$162.59	13.484%	$184.5136	$184.51	$184.50	$184.50
Purchase #7	$228.26	4.621%	$238.8079	$238.81	$238.80	$238.80
7 purchase totals =	$1,127.70		$1,196.7034	$1,196.69	$1,196.70	$1,196.70