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	$69.32	3.442%	$71.706	$71.71	$71.70	$71.70
Purchase #2	$44.39	7.215%	$47.5927	$47.59	$47.60	$47.60
Purchase #3	$49.58	13.163%	$56.1062	$56.11	$56.10	$56.10
Purchase #4	$146.91	13.206%	$166.3109	$166.31	$166.30	$166.30
Purchase #5	$35.58	7.839%	$38.3691	$38.37	$38.35	$38.40
Purchase #6	$32.79	4.662%	$34.3187	$34.32	$34.30	$34.30
Purchase #7	$171.72	10.699%	$190.0923	$190.09	$190.10	$190.10
7 purchase totals =	$550.29		$604.4959	$604.50	$604.45	$604.50