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	$196.34	9.257%	$214.5152	$214.52	$214.50	$214.50
Purchase #2	$94.82	13.405%	$107.5306	$107.53	$107.55	$107.50
Purchase #3	$57.44	3.762%	$59.6009	$59.60	$59.60	$59.60
Purchase #4	$89.59	6.242%	$95.1822	$95.18	$95.20	$95.20
Purchase #5	$112.59	9.301%	$123.062	$123.06	$123.05	$123.10
Purchase #6	$131.26	4.119%	$136.6666	$136.67	$136.65	$136.70
Purchase #7	$60.66	9.715%	$66.5531	$66.55	$66.55	$66.60
7 purchase totals =	$742.70		$803.1106	$803.11	$803.10	$803.20