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	$56.26	9.311%	$61.4984	$61.50	$61.50	$61.50
Purchase #2	$24.45	3.217%	$25.2366	$25.24	$25.25	$25.20
Purchase #3	$70.85	3.871%	$73.5926	$73.59	$73.60	$73.60
Purchase #4	$247.30	7.873%	$266.7699	$266.77	$266.75	$266.80
Purchase #5	$198.80	6.258%	$211.2409	$211.24	$211.25	$211.20
Purchase #6	$127.28	3.233%	$131.395	$131.40	$131.40	$131.40
Purchase #7	$124.83	13.210%	$141.32	$141.32	$141.30	$141.30
7 purchase totals =	$849.77		$911.0534	$911.06	$911.05	$911.00