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	$181.64	12.677%	$204.6665	$204.67	$204.65	$204.70
Purchase #2	$66.44	11.789%	$74.2726	$74.27	$74.25	$74.30
Purchase #3	$90.52	4.286%	$94.3997	$94.40	$94.40	$94.40
Purchase #4	$96.61	9.194%	$105.4923	$105.49	$105.50	$105.50
Purchase #5	$99.33	6.507%	$105.7934	$105.79	$105.80	$105.80
Purchase #6	$99.54	4.544%	$104.0631	$104.06	$104.05	$104.10
Purchase #7	$18.96	9.737%	$20.8061	$20.81	$20.80	$20.80
7 purchase totals =	$653.04		$709.4937	$709.49	$709.45	$709.60