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	$199.89	3.640%	$207.166	$207.17	$207.15	$207.20
Purchase #2	$146.53	4.300%	$152.8308	$152.83	$152.85	$152.80
Purchase #3	$156.64	7.626%	$168.5854	$168.59	$168.60	$168.60
Purchase #4	$35.38	10.598%	$39.1296	$39.13	$39.15	$39.10
Purchase #5	$173.30	6.432%	$184.4467	$184.45	$184.45	$184.40
Purchase #6	$42.80	3.724%	$44.3939	$44.39	$44.40	$44.40
Purchase #7	$136.82	10.153%	$150.7113	$150.71	$150.70	$150.70
7 purchase totals =	$891.36		$947.2637	$947.27	$947.30	$947.20