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	$62.85	12.845%	$70.9231	$70.92	$70.90	$70.90
Purchase #2	$65.83	11.558%	$73.4386	$73.44	$73.45	$73.40
Purchase #3	$212.78	12.346%	$239.0498	$239.05	$239.05	$239.00
Purchase #4	$225.54	7.228%	$241.842	$241.84	$241.85	$241.80
Purchase #5	$64.26	4.764%	$67.3213	$67.32	$67.30	$67.30
Purchase #6	$111.78	13.639%	$127.0257	$127.03	$127.05	$127.00
Purchase #7	$201.37	10.286%	$222.0829	$222.08	$222.10	$222.10
7 purchase totals =	$944.41		$1,041.6834	$1,041.68	$1,041.70	$1,041.50