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	$154.82	6.548%	$164.9576	$164.96	$164.95	$165.00
Purchase #2	$95.87	5.262%	$100.9147	$100.91	$100.90	$100.90
Purchase #3	$23.75	3.595%	$24.6038	$24.60	$24.60	$24.60
Purchase #4	$104.61	7.585%	$112.5447	$112.54	$112.55	$112.50
Purchase #5	$41.62	5.283%	$43.8188	$43.82	$43.80	$43.80
Purchase #6	$197.31	7.767%	$212.6351	$212.64	$212.65	$212.60
Purchase #7	$137.55	5.210%	$144.7164	$144.72	$144.70	$144.70
7 purchase totals =	$755.53		$804.1911	$804.19	$804.15	$804.10